Where do those damn atoms go?

[04/23/10 Edit: If you came across this post by Googling to find out how many of our bodies’ atoms are replaced each year, would you drop me a comment and tell me WHY? I’m intrigued by the fact that so many people hit my blog by searching on this specific question! Thanks.]

Mark Jones left the following interesting question in another thread and I thought it was worth starting a whole new post in reply, because I’m often asked this question and I’m sure people would like to discuss it or at least hear me expand on it:

“Richard Dawkins intriguingly quoted you in his recent book, The God Delusion, “not a single atom that is in your body today was there when that event took place…” meaning, that every atom in the human body is replaced within our lifetime. I have read this assertion many times, but it’s source is never attributed. It is a facinating if true but I don’t want to quote it unless I’m sure of its scientic origins. Who can be cited?”

I can’t cite any single definitive authority, although see the last paragraph below. For my part I draw the conclusion from a whole bunch of evidence.

The first thing to say, though, is that it ISN’T ABSOLUTELY TRUE. Not quite. Not as an irrefutable and precise fact. I didn’t say it in the first place to declare a free-standing scientific fact but to add emphasis to an important but otherwise hard to believe point, and that point is still true even though I may have exaggerated by an atom or two.

The reason it can’t be true is actually supportive of my main point, so I might as well admit to it. It’s often pointed out (and again I can’t quote a higher authority on this) that statistically speaking, any glass of water you drink is likely to contain one or more water molecules that were previously drunk and later excreted by, say, Isaac Newton. Since water makes up a large percentage of our tissues, your morning coffee probably contained a molecule or two that was once an active part of Newton’s brain.

Logically speaking, therefore, you probably also have some atoms/molecules that were in your own body on the day you were born but then were excreted, recycled through rivers and seas, the sap of trees and the bodies of other creatures, only to turn up a second time in your food.

But this doesn’t alter the fact that all these molecules are transient parts of you. You are a system in flux; a pattern and not the sand in which the pattern is drawn; you are not the stuff of which you are made, and this was the point I was trying to make in my book.

Nevertheless, people still don’t believe me, so I need to counter some potential objections. The thing that makes it so hard to believe in the first place is the intuition that we absorb food, excrete most of it but retain a little, growing as we go. I’ll deal with some trickier examples in a moment, but in general this just isn’t true. Biological molecules don’t tend to last very long and need to be replaced. That’s why every cell’s DNA is kept so incredibly busy making new proteins. We grow when the input outweighs the output, that’s all.

Not only do whole cells die in their millions and need to be replaced, but individual molecules in those cells are constantly being recycled and repaired. Even the DNA itself. We have no problem recognising that our hair and fingernails look the same from day to day yet are constantly being replaced, but it’s harder to see this going on inside the cell membrane so we find it hard to believe. Yet every cell is engaged in a constant struggle to maintain itself against decay, not just day to day but second to second. It consumes a lot of our energy.

“What about brain cells?” people say. “I’ve heard that neurons aren’t replaced once we become an adult.” Well, until recently we didn’t think that adult brains produce new neurons but we now know this isn’t true. Maybe the new neurons go on to add new matter and not “replace existing memories”, but our brains don’t get heavier so it seems to me most likely that the new cells take on connection patterns similar to existing ones, which later die. The memories and mental functions remain but the neurons that represent them change over time.

Either way, just because a given neuron stays around for many years, this doesn’t mean the cell is made from the same molecules all that time. Just like any other cell (and neurons are especially metabolically active) they consume energy to maintain themselves against decay and repair themselves from damage. Keep taking those antioxidants, because oxidation due to free radicals is one way in which the components of cells are repeatedly being broken down.

“Alright then, so soft tissue is constantly being replaced, but what about bone? People exposed to radioisotopes like Strontium absorb it into their bones and the radiation from these can still be detected many years later, so bone must be a permanent fixture, surely?”

Ok, you kinda got me on the Strontium, maybe. Same with lead. But not the bone. Bone is constantly being broken down, not just by the ravages of time but by cells called osteoclasts. And new bone is constructed by osteoblasts to replace it. This deliberate destruction of body tissues is more the rule than the exception: the body is maintained in a dynamic equlibrium, between in-built destructive and constructive processes. If it weren’t then it couldn’t adapt, and adaptation is the name of the game, even for bone. You only (!) have to go into space for a few days, or lie in a hospital bed for a few weeks, to see your bone mass drop substantially as the constructive forces are slowed (because the body thinks they’re now an unnecessary waste of energy), leaving the destructive forces to set a new balance.

And about that Strontium. I imagine it’s probably true that you can pick up a little radiation for years after exposure (although I don’t know for sure that it is retained for a lifetime, and the retention still has a half-life [a chemical half-life, independent of the radioactive half-life], so all of it would be removed if you lived long enough). But that doesn’t mean the Strontium atoms are in the same bits of bone from moment to moment. Calcium, magnesium and elements that mimic them get removed from bone all the time by osteoclasts, and much of it gets re-used to make new bone. Some of the minerals in bone do take a long time to leave the body but they’re still being recycled (resorbed) all the time, and that’s all I was trying to say.

Things get a bit more philosophical when we ask the question: “what does it mean for a molecule to be the same molecule anyway?” One of the things I was trying to get across in my book was that, not only are bodies processes or patterns, not “stuff”, but even stuff is a process. A subatomic particle is (I believe) a resonant state, not a little lump floating in space. An electron is conceptually more like a hurricane or the whirlpool that forms around your bath plughole – it’s a persistent disturbance in something (in this case a “field”). It’s more like the ringing of a bell than the bell itself. And is the sound you hear from a bell now the same sound you heard a moment ago, or is it a different ring that simply sounds the same as the previous one? When you start to look at particles, and therefore atoms and molecules, as self-preserving dynamic states, the whole concept of static “sameness” ceases to be meaningful.

What I was trying to do in Creation was to dismantle our intuition that the universe is made of (a) “real stuff” and (b) mere patterns in that stuff, by showing that even the real stuff is patterns too. There’s therefore no fundamental distinction between, say, mind and matter. It’s not that matter is somehow real and physical, while mind is not, they’re just different levels of self-maintaining pattern. Nor do we need to invent a special kind of (dualistic) reality for mind. And I then went on to assert that, when the processes that we think of as “real things” in the so-called physical universe arise inside a virtual universe in the same fashion, then we have to consider them just as real. Artificial life can therefore (under the right circumstances) be real life. But that’s a long argument and one book wasn’t nearly enough to do it justice.

So that’s the reason I made the assertion about the total replacement of our bodily atoms. I may have overstated it – there may be a few atoms that still ring like the same bell all our lives, but it’s more of a statistical accident than anything else. The central point is that our bodies are in constant flux. We are not the stuff of which we are made; we are a self-maintaining pattern in a constantly changing substrate.

I hope you’ll agree, because I think that once we rid ourselves of our innate dualism, the whole universe takes on a very different and much more creative look.

So I can’t cite a single definitive authority, but the evidence for the principle of constant renewal is out there in spadefuls. Someone once sent me a link to an NPR story that discusses some of this, and that does quote some specific experiments that show 98% of our bodily mass being replaced each year. Now, assuming this doesn’t mean that everything that could be replaced is totally replaced inside a year but 2% remains forever indelible, then if 2% remains after one year, only 2% of that 2% will remain the second year. When you get to be as old as I am, that brings it down to 1E-83 of a percent, and yet our bodies only contain something of the order of 1E29 atoms. So that suggests we are totally replaced many, many, many times over, and any atoms we have now that WERE in our body on the day we were born are almost certainly back for their second or third appearance!


About stevegrand
I'm an independent AI and artificial life researcher, interested in oodles and oodles of things but especially the brain. And chocolate. I like chocolate too.

187 Responses to Where do those damn atoms go?

  1. hammyhamster says:

    Wd like to get your views re AI for a feature I’m doing; do you have an email address?
    Robert Matthews, BBC Focus magazine

  2. J.D. says:

    That was a long answer, though I’m not sure that I’m too keen on your insinuating that I eat myself. Either way, people who don’t believe you are probably in the same camp of people who think we use 10% of our brains, because they recall hearing it at some point or other..

  3. Stark says:

    This is wonderful, Steve. And it was something I’ve been meaning to ask you to write more about. Great examples! I wish I were able to visualize it easier. The way I kind of see life, or a description of life is that, if you look at tv static, or random pixels on a screen, life would be somewhere inbetween the intense randomness and boring order of a turned off screen, or a static rectangle. I don’t really know how to describe it, but it’s definitely something I’d like to describe!

    • stevegrand says:

      Hey Stark,

      Thanks! Are you aware of Chris Langton’s notion of the “edge of chaos”? That sounds like exactly what you’re talking about – the tiny region between boring order and meaningless randomness, where all the interesting stuff (computation, life) takes place. He coined the term in relation to a particular measure in cellular automata, and this is somewhat disputed, but as a general metaphor I think it’s very useful.

  4. Stark says:

    I hadn’t read into it deeply until now, but I think this is exactly what I’m trying to say!

    It’s an interesting foundation for a study in what is required for a minimal life-form (or what would be required to simulate one!). I’d love to write an origin of life simulator based on a sort of artificial chemistry (much like http://organicbuilder.sourceforge.net/applet )
    The way I see it, if you had a simple-yet-dynamic chemistry/energy field simulation capable of feedback and interactions, simple life could appear that would be realistic to some degree.
    Of course, it wouldn’t have to be that realistic — a lot of the chemistry interactions could be assumption-(optimization)-based. Just a neat thought, I play with the idea, but I haven’t had too much free time to really get serious about it.

    I was kind of hoping Spore would contain something more realistic in this sense. Too bad… Maxis had to make it “fun”, EA lost it’s soul ages ago. (Remember back when things like M.U.L.E. made EA seem cool?)

    Anyway thanks for replying, and welcome to the States. (Sorry if it’s a bit crowded and irrational, I’ve not had much say in either regard)

  5. stevegrand says:

    If you can get from plain, clearly non-living (and not too obviously “poised for action”) chemistry, to simple living systems capable of metabolism and evolvable self-replication, then you’re probably up for a Nobel prize!

    That’s not to put you off – far from it. It should be doable. It MUST be doable. But nobody has yet actually done it. Few have even tried (except in part, such as the formation of micelles) but it needs doing to demonstrate that life CAN arise spontaneously out of non-life, at least in silico.

    You might like to join the Biota mailing list if you haven’t already. You’ll find a lot of people interested in the same things. Go to http://www.biota.org – there’s a mailing list link on the menu.

  6. Stark says:

    Here’s work by the same guy who did the Artificial Chemistry on proto-cellular life simulations: http://www.sq3.org.uk/papers/cells2007.pdf

    Tim J. hutton is his name, and his main website is: http://www.sq3.org.uk/wiki.pl

    I do believe I emailed him a while ago just to congratulate him on the fine work.
    I think he’s farther ahead in this work than I! 😉

    (sorry if this is a double post, something acted weird)

  7. Stark says:

    Sorry, I forgot to post what he is currently working on (via his blog): http://code.google.com/p/latticegas/

    (You can delete this post if you need, I’m just sending to you really — maybe I should be emailing you :))

    • stevegrand says:

      Great paper! I know Tim’s name but I don’t think we’ve met. He’s got further than I thought anyone had. The chemistry is understandably still a little bit “poised”, but it’s very nice nonetheless. Thanks for that.

  8. Pingback: We are Patterns not Souls « The Sublime, Weird and Unfathomable

  9. russellx23 says:

    Welcome to virtual reality.

  10. stevegrand says:

    Hey wow! Ferkeltongs has read my WordPress comments!

  11. Pingback: Curious « Steve Grand’s Blog

  12. Neil Pakenham-Walsh says:

    Richard Dawkins, in the God Delusion, wrote (as I remember) that every single one of the atoms in our body is replaced every 9 years. None of the matter that is in our bodies today was there 9 years ago. He attributed this to Bill Bryson, ‘Brief History of Everything’.

    I checked out Bill Bryson, and he said this: ‘It has been suggested that there isn’t a single bit of any of us – not so much as a stray molecule – that was part of us 9 nears ago.’ Bill Bryson, Short History of Nearly Everything, p331. Bill Bryson attributed this to David Bodanis, another popular science writer.

    I checked out David Bodanis, and he said this: ‘Every nine years or so almost every single molecule that makes you has gone, either floated away or poured out.’ (The Secret Family, p89-90). Bodanis does not give a source/reference of any kind for this assertion.

    Is anyone aware of any *scientific* reference (rather than hearsay) to back up the assertion that our body is, in effect, replaced every 9 years?

    I asked this question on Bill Bryson’s forum – no answer. I’ll try ‘the horse’s mouth’ – David Bodanis – and will let you know if I hear from him….

    • stevegrand says:

      (Sorry about the delay – been offline)

      I think you may be getting mixed up about the sources. I don’t have a copy handy but I’m fairly sure Richard quoted me, rather than Bill Bryson. But the 9 year bit doesn’t come from me. All I said was that we are not made of the same stuff we were as a child.

      Several different mechanisms are at work replacing our molecules (as I discussed in this post), and all of them are probablistic. So, like radioactive decay, each mechanism will have a half-life. That makes any fixed time period fairly meaningless, so I’ve no idea where the 9-year estimate comes from. I’d guess someone found an estimate of the half-life of one such mechanism and then extrapolated until, say, 99% of the molecules have been replaced using that method. There’s always a finite probability that one or more molecules remain indefinitely, or even return to their former owner. Nevertheless, there’s no doubt at all that biology is constantly recycling matter, as proteins break down, bone gets consumed and rebuilt, minerals get moved from storage, cells die, metabolism takes place, etc. Some of these processes have half-lives in the order of minutes, some in the order of decades. It would be very hard to combine all these factors to come up with an average half-life, let alone designate a specific interval by which “all” molecules have been replaced. It would be difficult to radioactively label all significant elements to determine the overall half-life experimentally. But there’s no question that we are systems in constant flux and the bulk of our substance is replaced quite rapidly – that’s why our genes are kept so busy producing new proteins.

      I cited an NPR story that says this: “In a study published in the Annual Report for Smithsonian Institution in 1953, scientists found that 98 percent of our atoms are replaced each year.” But I don’t think it really needs defending experimentally – it follows logically from all that we know about biology. The precise rates don’t much matter – it’s the principle of autopoeisis that’s important, I think. For interesting reasons this seems to bother many people, sometimes to the point of getting hot under the collar, but it’s just a fact about biological systems, more-or-less as it is a fact about rivers.

      • Jake Reed says:

        “But I don’t think it really needs defending experimentally — it follows logically from all that we know about biology.” –> As an MD/PhD student at a very prestigious university, this statement is completely wrong. The human body is an extremely complex molecular/physiological machine and EVERYTHING needs to be defended experimentally, especially things that you might consider follow logically. I mean just imagine if this was the rationale of the FDA in approving new pharmaceuticals. The only reason clinical trials get funded is because they “follow logically” what we would consider to be excellent drug targets with mounds of animal testing.

        Neurons do NOT REGENERATE! Especially those involved in the corticospinal tract (voluntary muscle control), if you have an explanation for how these neurons are replaced throughout an individuals lifetime, then I have an unlimited amount of money I would like to invest in your start up pharmaceutical company. Even if the lipids, cholesterol, and proteins in their membranes are replaced periodically, their DNA is NOT. At most throughout a corticospinal tract neuron’s lifetime a small percentage (<10%) of the DNA bases will be replaced through DNA repair mechanisms, but if the percentage is much larger than that I would be very surprised.

        Bone and enamel in teeth are NOT replaced at any significant rate, osteoclasts and osteoblasts are mostly active during GROWTH and MAINTENANCE (as in at the ends of the growth plates throughout your life, not along the length of the bone). Finally, glial cells regenerate constantly; however cortical neurons DO NOT, cortical neurogenesis is only known to occur in the hippocampus (memory) and olfactory bulbs (smelling). This is proven everyday by ER physicians and neurologist in the maintenance and treatment of stroke victims. Again, if you know how these cells regenerate or have a valid, experimentally proven hypothesis, I have unlimited sums of money to invest in your start up medical research company which will put us both on FORBES top 200 list.

      • stevegrand says:

        Well thank you for your opinion. And for shouting it at me. I don’t frankly give a fuck how prestigious your university is, and I’m not the least bit impressed by PhD students. None of the things you’ve mentioned invalidate anything I’ve said. I’m not arguing that all cells are replaced wholesale – they’re replaced at the molecular level. And as I explained, I’m not trying to make a statement of absolute fact – it was an illustration of something that has nothing whatsoever to do with medicine. But since you’ve been so condescending I think it’s best not to argue with you. Your comments are noted and I wish you luck with the bedside manner.

  13. Vegard says:

    Just a fun fact: I was watching Alan Kay’s OOPSLA keynote speech from 1997 ( http://video.google.com/videoplay?docid=-2950949730059754521&hl=en# ) and at about 46 minutes into it he speaks about the growth of the ARPANET:

    “As far as anybody can tell, I talked to Larry Roberts about this the other day, there is not one physical atom in the Internet today that was in the original ARPANET, and there is not one line of code in the Internet today that was in the original ARPANET. […] So this is a system that has expanded by a hundred million, has changed every atom and every bit, and has never had to stop.”

    • stevegrand says:

      Ha! That’s nice. When it comes down to it, MOST “interesting” systems in the universe are in constant flux. They’re thermodynamically open and that’s what makes them able to do interesting things. I hadn’t thought of the Internet, though. Cute! Thanks for the quote.

  14. Tim says:

    It is a very curious thing for me, having an almost obsessive nature to understand the detail of how things work. I recently found a website which outlines an honest-to-god religion based on particle physics that I believe to be plausible. I’ve not yet found any other matter on this view anywhere on the internet. If nothing else, it does make for interesting reading.

    • stevegrand says:

      Hi Tim,

      Thanks for the link. It’s interesting, mostly because they start from roughly the same position as me and end up with the exact opposite conclusion! I find these sorts of theories very exasperating, to tell the truth. I can see the DESIRE to make consciousness some sort of primal element of the universe, but they dodge all sorts of questions in doing so. I personally think they’re missing the point. I think consciousness is a real thing but it’s an invention – a discovery – of the universe, NOT something that’s always been present and exists in every particle.

      To me, the ‘primal consciousness’ view doesn’t make sense and rather demeans consciousness. If consciousness is so elemental, surely that makes it trivial? It turns it into a bland, structureless, simple entity like electromagnetism. What I think people are missing is the distinction (or lack thereof) between substance and FORM. Form is the structure of matter, not the matter itself (actually I argue that matter itself is also form, but that’s a longer story). Structure is what gives rise to life and to minds. Consciousness EMERGES from interactions. Once there was no consciousness in the universe and now there is. Just as there was once no matter in the universe and now there is – the two are highly analogous events. The universe is constantly discovering new levels of phenomena. Each class is a variety of form – a way of arranging elements at a lower level so that the new arrangement persists over time (e.g. by self-maintenance). Each is a valid new form of existence.

      The snag with my emergent viewpoint is that it doesn’t have that nice “everlasting life after death” thing. Their primal consciousness “continues” in some dissipated form. We’re supposed to feel better because, although our brains have rotted away the sum total of consciousness is still “there”, because it’s elemental and a fundamental part of the atoms that were once our brain. I can’t offer that comfort, although personally I don’t really find it very comforting anyway.

      This, incidentally, is a major reason why the primal idea must be wrong. A brain is made from atoms of carbon, hydrogen, etc. They say each of these atoms is an example of the same thing – an ‘eternon’ – and all eternons carry a little bit of consciousness. But a brain can be made unconscious without losing any atoms – just by rearrange them a little, perhaps with an anesthetic, perhaps with a bullet. So how can they argue that a dead brain and a live brain contain the same amount of eternons and therefore the same sum total of consciousness, when everything we would normally define as consciousness is so radically different in each case? Why would a brain exhibit consciousness at all, when a cabbage doesn’t, despite them having roughly the same constituents? It doesn’t make sense. Whatever definition of consciousness they derive to explain this, makes a mockery of what we normally regard as conscious – we’d have to have a new definition for that, and THAT is the kind of consciousness we actually care about.

      I have some sympathy for their view that all matter is the same, but I think they’ve picked precisely the wrong “thing” for it to be. Matter is form – a disruption or arrangement of the electromagnetic and other basic fields that happens to be self-preserving. A mind is form too – an arrangement of neurons that happens to create another entity (another long story) which is also self-preserving. Sadly for us, as conscious entities, it’s generally only self-preserving for about 80 years, whereas a free proton can hang on in there for 6×10^33 years. But hey, a free neutron only lasts about 14 minutes, so we don’t do too badly! Once the form of a neutron is disrupted too far, it decays (producing simpler entities) and isn’t a neutron any more. Once the form of a mind is disrupted too far, it’s not a mind any more either. Eternal life would be lovely, but it’s problematic.

      I also have a LOT of sympathy for the idea that rationalism can offer a new concept of spirituality – a better one than religion. But I think they’ve picked the wrong one because they’re being too reductionistic. Their sentiments about the beauty of the universe are admirable, though.

      I’m trying to develop a book on all this, hence my lengthy answer. So thanks for the link – like you say, it’s interesting and very relevant, even though I don’t agree with them!

      • stevegrand says:

        P.S. I just found some other bits of their website that I didn’t see the first time. On one level they DO seem to be struggling to explain emergence, but on the other they utterly fail to do so, imho. And the things they say about evolution are just plain wrong.

      • stevegrand says:

        P.P.S. Now I’m just really irritated with the whole notion. It’s basically Intelligent Design with a Distributed God. It’s a pile of crap.

      • sykickvision says:

        Wow, Steve. I had forgotten all about ever posting to you on here and then I found your reply. Thanks for doing so, if you remember, can you tell me exactly what parts of evolution it was that you noticed that Eternism got so wrong?

      • stevegrand says:

        It’s just plain gibberish, through and through. “An ancestor of the giraffe was born accidentally with a long neck”??? Humans evolved from Amoebas? Natural selection doesn’t necessarily produce “higher organisms”? What’s a higher organism, for heaven’s sake?

        It’s all arguing backwards from mistaken assumptions and ignorance. Exactly the same conceptual mistakes that lead to creationism. For instance, one of the unquestioned assumptions is that species have got “better” over time; that there’s some kind of “progress” involved. Humans are somehow “better” than amoebas. Try asking a horseshoe crab what it thinks of humans being better than it – humans have only been around since last Wednesday! We prize our intelligence but the jury is still out about whether intelligence is a good adaptation, let alone that it’s somehow better than having sharp teeth or the ability to metabolize methane. From OUR perspective, humans are great. But we would think that, wouldn’t we? From the perspective of bubonic plague you’d get a different answer. Living things adapt to a niche, that’s all, and as more niches get adapted to, they create still more niches. Hence life diverges. Many of these secondary niches involve making a living out of other creatures, and hence life tends to get more complex. But so what? It’ll get simpler again at the drop of a hat, if the opportunity arises. Just because evolution seen from our “end” of it seems like progress, it doesn’t mean a thing. But this is a major unquestioned assumption on the part of the author. He or she is not satisfied that natural selection accounts sufficiently for this presumed progress (almost entirely because they don’t understand natural selection) and so there “must” be a better explanation.

        Their ultimate conclusion is an example of exactly the thing they’re trying to argue against – it’s a materialistic, reductionistic hypothesis of the worst kind!

      • Ellen Winner says:

        Dear Steve – I got to your site because, having heard that our bodies replace our atoms fairly often (I guess the estimates run from 1 to 9 years), I started to wonder if inanimate objects also replace their atoms that often, or if not, how fast do they replace them? I didn’t find an answer though.

        PS, Based on my experience Consciousness is primary. It may use matter patterns to think complex thoughts, but it pre-exists any particular thoughts.

      • stevegrand says:

        Thanks Ellen. Some non-living things replace their atoms, although maybe we shouldn’t then call them inanimate! Clouds, dunes, rivers, fires… It depends what you call a “thing”. We think of ourselves as single things but really we’re a hundred trillion single-celled creatures!

  15. dOminic says:

    Hello steve,

    I am very new to this blogging, I even believe is it my first commentreply on one.

    The reason I am commenting is because in the second place you ask people to send a comment and let you know why they search for this information.

    Well I can be very fast and simple with this, if you don’t experience any interest in your body and never wonder how things became how they became, I believe you will never understand yourself and along all the things you do or say.
    So to me it is very important to try figuring out as much as I can.. Have to say I don’t spend all my time on this, but whenever I am in deep thoughts and created the right question in my brain, I google it and explore.

    So now my first place question..

    Who are you and what do you do ?

    I couldn’t find information about you here at this blog.. Have to say I am using my iPhone so that might be the reason..

    • stevegrand says:

      Thanks Dominic! I agree with what you say. So what exactly was the question you asked that brought you to my page? I have a feeling a lot of people get here because they heard one of Richard Dawkins talks, or read his book, where he quotes me. Is that what brought you?

      Who am I? I’m just someone who asks a lot of questions about how things became what they became, too! I’m an amateur scientist and I work in artificial intelligence and artificial life. I’m interested in the nature of life and how minds come into existence. I also write computer games occasionally, to try to explore these questions. I once wrote a game called Creatures, which became quite popular and showed that many other people are interested in these questions, too. Since then I’ve written a couple of books and built a couple of robots, but it’s not an easy way to live, so I’m now writing a new artificial life game to test out some of my latest ideas and hopefully make a bit of money at the same time! Here’s some stuff about me and the Creatures game: http://creatures.wikia.com/wiki/Steve_Grand

      Thanks for letting me know how you got here!

  16. John says:

    I just wanted to make a quick comment as you requested. A friend of mine posted the 98% statistic on Facebook as a random fact, and I started looking around online to check it out. That’s how I stumbled across your page. Your answer has turned out to be a very nice compilation of the opinions on the matter I’ve found elsewhere. Thanks!

    • stevegrand says:

      Aha! Thanks, John. So between Richard Dawkins quoting me and some unknown source of random facts that’s probably enough to explain it. It’s still one of the most common search terms. Thanks for the feedback!

      • Neil Pakenham-Walsh says:

        Richard Dawkins did not quote you, he quoted Bill Bryson. Bill Bryson in turn quoted another popular science writer, David Bodanis. David Bodanis didn’t quote anyone, nor did he give a reference. In other words, these three people are not offering any evidence for what they are saying. The original statement could just as well have been written by J K Rowling or Hans Christian Anderson!

      • stevegrand says:

        Richard may well have quoted Bill Bryson too, certainly if the number 98% was mentioned (which is traceable to the NPR story cited above). But Richard quoted the “Do you remember your childhood?” illustration from my first book in “The God Delusion” and also in a TED talk (http://www.youtube.com/watch?v=1APOxsp1VFw – the relevant bit is about 10 mins in). We also discussed the basis behind it at some length, because people were asking him. So I’m guessing this may be one of the reasons for the search term, because “98%” is almost never mentioned.

      • stevegrand says:

        Addendum: Finally I’ve managed to get hold of the original 1953 Smithsonian report mentioned in the NPR article. Unfortunately it’s still not primary, and no references are given. It’s in a long article on radioisotopes and the relevant quotation is:

        “Tracer studies show that the atomic turnover in our bodies is quite rapid and quite complete. For example, in a week or two half of the sodium atoms that are now in our bodies will be replaced by other sodium atoms. The case is similar for hydrogen and phosphorus.
        Even half of the carbon atoms will be replaced in a month or two. And so the story goes for nearly all the elements. Indeed, it has been shown that in a year approximately 98 percent of the atoms in us now will be
        replaced by other atoms that we take in in our air, food, and drink.”

        The elements mentioned are all easily available for tracer studies, but they’re also things with relatively low residence times and no mention is made of how the overall figure was derived. The information clearly holds good for proteins, at least, so that’s the bulk of us.

  17. Ciarán says:

    I don’t know if you are still intrigued by why so many people are looking for this answer. I get an uncomfortable feeling in my gut when I can’t understand something that feels counterintuitive. An example would be speciation. I wrecked my head trying to figure it out chicken and egg style after a Christian friend of mine said something like “but every animal in a species would have to spontaneously change at the same time for evolution to be true!”. I knew it was nonsense but couldn’t explain it at the time. Eventually I sat down and read Gould, Shubin and especially Dawkins. I think it was in River Out of Eden he explains speciation as process rather than an event.

    This atom thing is the same. It doesn’t sit right and it’s bothering me. (I’m deliberately writing this before I find the answer and become pompous…) Do they mean every cell? If they do I could cope with that with very little to question. But every atom is a different thing. I want to know what is meant by that exactly: Is it a case that by saying every atom they just mean thath as the cells are replaced its obvious the atoms are replaced too or do they mean something else? What about teeth and hair? Do they mean something like particles colliding with us shunt other particles out, an idea I’d want to see some pretty serious evidence for?

    I’ve heard some fairly silly esoteric or alt-med theories trot this “seven years” thing out, so I’m automatically suspicious as to what they think they mean when they say it.

    • stevegrand says:

      Thanks Ciaran. So have you found the answer and become pompous yet? 😉 The seven year thing is simplistic nonsense, as you say. It’s a half-life thing, so a cut-off date is meaningless. But atoms are being replaced independently of whether the actual cells are dying – cells are like the overall organism: *patterns* of molecules that persist even though the molecules themselves are merely passing through. Cells put a huge amount of energy into metabolism for good reasons – they’re constantly rebuilding themselves. Hair’s not a problem because it grows out. Teeth are much more dynamic than people tend to think. Most tissues are in a constant tension between destructive and constructive forces – even bone. I’d say it’s perhaps not an absolute fact – there may still be a few atoms that hang around for a lifetime – but on the whole we are persistent eddies in a perpetual stream of matter, which is the point I was trying to make and Richard Dawkins picked up on.

  18. Pingback: Me, Myself and I « Prickly Goo

  19. Hi Steve, why the interest. It wsn’t the number of atoms that interested me, but the fact that they change. I have never really believed cells don’t replicate…it just doesn’t make sense. Anyway, the reason for my interest is my daughter. She was born prematurely 20 years back, and has a left side hemiplegia, which is cerebral palsy. Anyway, the condition never imprves, unlike stroke victims, or closed head trauma victims.

    So her body re-makes itself, but doesn’t get better, not that’s counter intuitive! So why? Well it appears to me she has no map the new bits can follow which causes repairs to happen as it happened at birth, too early for a pre-existing map to help the regeneration process regenerate in a useful way. It seems if there was a way of superimposing the map, then some positive re-generation should take place.

    • stevegrand says:

      Thanks Gerard. That’s a pretty unusual reason to wonder! I’m really sorry to hear about your daughter. Is it spastic hemiplegia? All neurons rebuild themselves molecule by molecule, but when they develop their initial connectivity they tend to follow some form of scaffolding or chemical gradient. I guess the scaffolding is no longer there, so the nerves don’t know where to reconnect. It does seem quite plausible that they can develop the right connections later, though, so I should think there’s a realistic hope as people discover more about neurogenesis and neural plasticity. Good luck with the hunt! If I ever come across anything useful I’ll send it your way.

      • Hi Steve, is not spastic as such, it is a hemi though, but under the Cerebral palsy banner rather than spasicity which presents with a different set of issues that she experiences. Abi is quite mild, she has limited function in her left arm and hand.

        Her scaffolding, or map as I think of it, is missing, damaged and the regerartion follows the broken model. Seems to me re-teaching the non damaged model is the trick here, but of course how you do that is the problem.

        Thanks for the reply, and equally, if I come across anything of monumental import, I shall let you know!

  20. Calvin Moroe says:

    Hi. I came across your post from google looking up how many of our bodies’ atoms are replaced each year. You asked for a comment as to why.

    I am in the midst of a debate with a local Jehovah’s Witness who has been coming to my house for several months now because he doesn’t believe in a physical resurrection. It was a “fact” that came out in our last discussion: the physical body is replaced repeatedly throughout our life, so our bodies are not permanent. He believes, after death our physical body will be rendered inert and will not be used again at the resurrection, but that God will create for us new bodies to live in forever in paradise. I contend God will bring back together our physical bodies (DNA, atoms, cells, etc) and we will be the original person we were when we were alive.

    From my research, apparently, there are few cells in our body that remain for our entire life: those in the cerebral cortex and the heart. I came to this post, trying to track down a source for research done that followed radioactive atoms after they were fed to or injected into people.

    Hope this was what you were wanting to know.

    • stevegrand says:

      Thanks Calvin, that’s exactly the kind of thing I wanted to know. And I’d never have guessed at your particular reason.

      I can’t comment on your debate (fascinating though it is) because I don’t accept the thesis underlying either view, but I can tell you that although there are some cells that remain alive for long periods – maybe as long as our bodies as a whole – they’re still very much in flux. Each cell may stay around for a long time but the materials it is made from are constantly being replaced. In one of my replies to a comment on this post I gave a citation for some work on following radioactive atoms through the body, although unfortunately it was just a report to the Smithsonian in 1953 and doesn’t have any technical details. It suggested a 98% replacement of our matter within a year. I’m not sure what the significance would be for your argument, though. If you believe in a god and a resurrection and you believe it will be with your present body (I’d at least hope it was the body you had when you were twenty, not the one you had when you died!) then do you really NEED any physical evidence to support that? It seems to me you’re well past arguing from physical evidence long before you even get to that point.

      Anyway, thanks for the info. This is clearly an important topic for a wide variety of reasons! 🙂

  21. Julian says:

    Hi Steve,

    Just a note to say that I found this blog after searching for “richard dawkins every atom replaced”. The reason for the search was to find the TED Video that I wanted to show a friend. I raised the ‘fact’ that materially we are ‘replaced’ at an atomic/molecular level relatively frequently (I had the seven years in my head, no doubt a mental spillover from the classic cell replacement timeline).

    The reason that this interests me is that I have experienced states of ‘pure’ consciousness/awareness, similar I believe to those sought by Buddhists, meditation practitioners and other spiritual seekers. This expanded state of awareness reveals that fundamentally we are not what we appear to be on the physical level, but are the awareness itself, within which we (our bodies, identities) and everything else is experienced.

    Sounds very metaphysical, and to some, no doubt, a bit ‘out there’, but it seems to be a fundamental law of the universe, which as far as I can tell is also pointed to by quantum mechanics – the discovery that the observer and the experiment are one system, not separate.

    Many thanks to you and the other commenters for the fascinating discussion.

    • stevegrand says:

      Thanks, Julian! Funny that you were looking for this in support of what sounds like an Idealist position, perhaps even a solipsistic one. That’s a topic I plan to write a book about one day.

  22. Michael Vincenzo says:

    Dear Steve,

    Like some of the other posters, my search started with Richard Dawkins quoting you in his TED talk. It was a very powerful part of his speech. You obviously made quite an impact on him and his enthusiasm for your observation infected me.

    As for why care? On a merely scientific level, it’s a fascinating fact. The idea that our atoms come and go on such a frequent basis speaks volumes about our transient physical nature.

    It also dovetails nicely with other related observations, such as the ability to trace the percentage of corn based products a person eats by the amount of carbon 13 (vs. carbon 12) that is detected in a person’s tissue. As observed by Michael Pollan in The Omnivore’s Dilemma, a typical American has a rather high percentage of C13 in his flesh indicative of a diet high in corn based processed foods. He refers to us a corn chips with legs.

    On a more fundamental level, it adds dimension to the idea in psychology and neuroscience that our concept of “self” is partly or wholly an illusion. Our memories themselves are re-written each time they are recalled to the extent that the more times we revisit an experience from our past, the less “reliable” the recollected “fact.” Like many scientific truths, the idea of re-recorded, less reliable, memories of memories is somewhat counter-intuitive. But it is consistent with other processes going on in the maintenance of ourselves as a “pattern”, such as the DNA replication errors and cellular aging that define our mortality. So what are we really? If not the stuff our our present physical form, or even our very mutable memories, what does it mean to be me? My personal view, held by some cognitive neuroscientists, is that we are our narrative, our personal story that we repeat or revise as the case may be. I tell people, you are the story you tell yourself, so make sure it’s a good one! I’m interested to hear what you think. And thank you for working on this problem.

    Mike V.

    • stevegrand says:

      Thanks Mike,

      People coming here via Richard is a lot more understandable than some of the google searches would ever have suggested! I totally agree that we are the story we tell ourselves. Memories are important for making the narrative, even if they do mutate – the only way I wake up believing I’m the same person as I was when I went to bed is because of those memories. But I agree that it’s the continuity of narrative that matters. I’m still the same person I was as a child even though my memories have warped and my body has altered.

      There’s also an important sense in which all entities, alive or not, are systems in flux. Even electrons. But that’s a long story that I tried to sketch out loosely in my first book and still need to write a whole book about when I can get my head around it. Thanks for letting me know how you got here!

  23. Agnieszka says:

    I didn’t come on this website via Dawkins 🙂 I’m doing internship now in secondary school as a biology teacher and I found a piece in a students’ textbook saying that maybe the carbon in the bread you eat used to be Madonna’s hair, and I have heard before that the atoms are constantly being replaced in our bodies, so this time I had an urge to find an evidence, but unfortunately the only scientific source so far is this Smithsonian report from 1953 which is quite old and only thing I found so far. So I will be happy to see more sources.


    • stevegrand says:

      Haha! Madonna’s hair is a great example! Maybe your students could do a back-of-the-envelope calculation to work out if it is feasible? The most obvious way also involves the most sweeping generalizations, of course, but we could work out what fraction of the total biomass is now made from carbon from Madonna’s old hair clippings. Let’s say she has grown 1kg of hair in her lifetime and half of that by mass is carbon. The living biomass of earth is about 6×10^14 kg of carbon, I think. So if we assume the carbon from her hair is well mixed across the earth (big assumption, but close enough for a plausibility check) we can say that Madonna’s hair carbon makes up 0.5 / 6×10^14 of the biosphere, which is a bit less than 10^-15. So that means any random 12 grams of carbon in a chunk of bread will have that fraction of it having come from her hair. As long as there are enough atoms in those 12 grams for this fraction to be greater than one atom, we’re in business. Well, 12 grams of carbon contains 6×10^23 atoms (Avogadro’s number), so the fraction of it made from Madonna’s hair ought to be 6×10^23 x 10^-15, which comes to about six hundred thousand atoms! Have I done something really dumb in my calculations (I haven’t eaten breakfast yet!)? If not, it’s entirely reasonable to assume everything you eat has some of Madonna’s hair in it. A better calculation would involve a lot of variables but it would be interesting to try to figure it out. [Edit: I was out by a factor of ten – these corrected figures are closer, I think. Never do sums on an empty stomach!]

  24. bob says:

    just out of curiousity Why don’t tattoo’s get replaced by normal skin is some definitive time frame?

    • stevegrand says:

      That’s a damn good question! I’ve never thought about it, but it seems the answer is that the ink particles are large and get bound in place by scar tissue. The dermis itself doesn’t migrate to become the epidermis, as I understand it – there’s a special layer of cells above the tattoo that creates the epidermal cells. So I guess the dermis itself doesn’t have any movement that could migrate the ink particles back to the surface and they’re too large to be eaten by macrophasges and stuff. The dermal cells themselves will get turned over and resorbed, but the particles stay roughly in place. Which I guess is a good reason to suppose some actual body atoms might remain constant. Hmm.

  25. Bruno says:

    “drop me a comment and tell me WHY” Here I am, doing just that.
    I still hadn’t seen these theories on brain cell regrowth, so I believed my brain cells were the ones I was born with. Nonetheless, I believed the stuff the cells were made of were replaced during cell normal operation. Like circulating inventory stock or equipment maintenance, in a business analogy. I was googling for answers because I was thinking about what you put so well: I’m not the stuff that I am, I am the pattern that emerges among that changing stuff (what I understood of what you said). And my doubt was if that pattern could be linked to brain cells or their atoms, considering they are the same from as long as I can remember being me, or being the same pattern. Now, convinced that they aren’t the same as the ones I was born with, I only find more questions: Since my pattern isn’t linked to my brain, or my body or my atoms, what is it linked to? Nothing? Anything? Can my pattern influence or be influenced by something that doesn’t influence or is influenced by my body? I think memories are tied to the brain, i.e. if you lose some of your brain you might lose some memories, but that doesn’t make you any less you. Therefore, maybe my pattern existed before my brain, I just can’t remember it (not even hypnosis and the like should be able the work, unless the pattern could communicate with an external, metaphysical source of memory), and will continue to exist after this body has perished. But that goes way too much metaphysical for now.

    • stevegrand says:

      Thanks Bruno! Interesting questions. Regarding what the pattern is tied to, I guess there are two levels of answer. Practically speaking, a living thing’s pattern only remains as long as there is enough of it left to rebuild the missing part. Otherwise we die. So in that sense the pattern doesn’t have an independent existence, since if you remove all the matter it will be gone. Even the DNA is not enough without some cytoplasm to make use of it. So we are the same person from year to year only in the same way that we might say we’ve always had the same hammer, even though it has had two new heads and three new handles. On another level, although the pattern can only exist meaningfully in the presence of matter, even matter itself is just a pattern – the elements are all made of identical stuff, just arranged in different orders, and even electrons, protons and neutrons are patterns at several levels. So it’s maybe misleading to think of there being anything to tie it to, if you see what I mean! A living thing is a pattern in a bunch of patterns, which themselves are patterns in a bunch of patterns. Who knows how far down that remains true, but we have to be careful not to think of matter as somehow real, and patterns as somehow not, since matter is also a pattern. And if that doesn’t make your brain ache then you’re a better man than me! 🙂

  26. Johan Louw says:

    As a physicist that spent years studying Gauge theories and string theories I came to the conclusion that there simply is no matter as is currently the mainstream thinking, but only excited solititonic states of the luminiferous aether ( or some other version of space). An explanation of my reasons and thinking would be long and I will only write it for you if specifically request it. But it does not conflict with current well tested physics. It is just a better theory, or so I think, by applying Occam’s Razor. I am stuck on the details but maybe I’ll succeed with the mathematics one day and publish it. You can blame Dawkins for my introduction to you, because his description of your thinking resonated with my own view of what it is manifests itself as matter. Thank you.

  27. Thank you for such an interesting post, the reason you came up on my google search at 1am looking for info about my atoms changing, is that it gives me some comfort to think the atoms that create me now are different from the ones I that were my atoms when something really horrible happened to me and it goes with the idea of my neurons (if thats the right word) changing through psychotherapy. There’s just something magical and reassuring about the idea somehow.

    • stevegrand says:

      Wow! Now there’s a reason I never would have guessed. Well I do hope your new atoms and new neurons suit you better than the old ones. I can understand the sentiment, thinking about other people I’ve known who’ve had really bad things happen to them, but it had never really occurred to me before that there’s something reassuring about being renewed! Thank you for that. Sleep well.

  28. Jesse Mills says:

    You asked! So: I actually ended up here by googling the myth that all of the cells in your body are replaced every seven years, and then by following links from other sites until I landed on this one.

    The reason I was looking it up is because I recently read about the Swampman thought experiment, and then remembered the seven year myth today. If we’re made up of completely different atoms than we were in younger years, we’re pretty much all swampmen of sorts! I just thought it was interesting is all. So that’s why I’m here!

    PS: I really enjoyed the post. It was interesting. 🙂

    • stevegrand says:

      Thanks Jesse! I’d never heard of the swampman before. Philosophers do talk drivel! I’ll have to think harder about it, though. There are some atrocious semantic slips in it but it’s quite hard to pin all the mistakes down. Two different meanings of the word “recognize” are certainly part of it. Thanks for the heads-up! 🙂

  29. Pingback: On Buddhism, reincarnation, and Dundalk F.C. « Prickly Goo

  30. Vegard says:

    Just got this off Reddit: http://io9.com/5937572/remarkable-video-captures-the-flow-of-proteins-inside-an-individual-neuron

    “Your brain is being disassembled and reassembled every day,” said study co-author Don Arnold in statement.

    “One week from today, your brain will be made up of completely different proteins than it is today. This video shows the process. We’ve known that it was happening, but now we can watch it happen.”

    • stevegrand says:

      Wow! That’s fantastic! It makes perfect sense when you think that our DNA is constantly active, constantly making proteins. But the turnover rate is way higher than I’d ever have guessed.

      I think we tend to make (be implicitly taught) two conceptual mistakes: One is that DNA is a program that is only run once, to create us; the other is that “structural proteins” means something like the wall of a house, rather than something more like scaffolding. Or at least, those are two things I have to keep reminding myself aren’t true – I can’t really speak for anyone else. Really the DNA program is being run many millions of times a day, churning out scaffolding that only lasts for an hour or two and needs to be replaced. It’s not the image we tend to take away from school biology, is it?

      Thanks for the link! QED, I think. Point proven.

  31. John Petersen says:

    I had seen you quoted in Dawkins’ book and read your statement as part of a worship service at a Unitarian Universalist church. I’m a chemist by training and knew from my biochemistry that some components of the body (water) turn over quickly while others do not. A nice article could be written entitled “a river runs through you” as values for inputs (beverages, food) and outputs (urine, sweat, exhalation) are well known (water labeled with deuterium or tritium was used for the studies). Interestingly, the rate of water turnover varies with age, see p90 http://www.nal.usda.gov/fnic/DRI/DRI_Water/73-185.pdf
    The question of tissue turnover is important to a variety of pharmaceutical studies so values for bone and various soft tissues have been published. A nuanced description of turnover would start with water and then move to ions (chloride, phosphate) then to small molecules (like glucose or ATP) and then macromolecules (proteins, RNA) and DNA. Finally one would look at structural elements like collagen, bone and teeth which have slower turnover.
    For the statistics buffs, statistically not every atom in a cell will turnover (even if one assumes perfect mixing). So some part of us is new, but there are always some “old” atoms & molecules hanging around.

    • stevegrand says:

      Thanks John. It never occurred to me to turn to the pharmaceutical literature! Of course, bodily turnover doesn’t count internal turnover. Even bone is constantly being broken down and rebuilt, with two cell types perpetually devoted to the task, so even though the Ca++ ions might hang around in the body as a whole for a while they aren’t necessarily in the same place for very long. I like the river analogy! Real rivers are just on the edge of the class of thermodynamically open, self-organizing systems like organisms, so the analogy works several ways.

  32. Alex says:

    “drop me a comment and tell me WHY”. A few days ago I was reading an interesting (for ne) discussion about Star Trek teleportation. Some people argued about teleportation not being possible because you would basically make a copy (although perfect is still a copy) and destroy the original, while the argument against this was that we are basically changing over time until each atom gets replaced in our body (destroying the original also, but much more slower) and that the teleporation will follow the same process but in an instant instead years or decades.

    Of course, this discussion got me thinking and I started to look for scientific proofs. Haven´t found anything till now, but your post was a nice read.

    PS: I´m usually the type who prefers to read than getting involved in discussions over the internet. However, this time I decided to reply simply because you wrote WHY with capitals 🙂 I just felt you are genuinely curious about why people would be interested in such things

    • stevegrand says:

      Haha! Yes, I am curious. Thanks for that. The Transporter problem is a great way to trip up our innate Cartesian dualism, I reckon. I don’t see how anyone can argue that teleportation isn’t POSSIBLE on that basis; just that it wouldn’t be terribly practical because it would create two of you. Or one of you would get killed in the process. I can’t see any reason in principle why a scanner couldn’t scan the properties of every atom in our bodies and assemble a new copy somewhere else, who would believe he had traveled as a result. Meanwhile, the other copy would feel like it hadn’t worked, because they are still standing where they started, feeling foolish. It really challenges our idea of personal existence and shows how we are who we are, purely because we have the memories of who we once were. Mind-wrenching stuff!

  33. Dick Lawrence says:

    you asked, so … here it is. On what’s probably the most intelligent site covering global energy issues – TheOilDrum.com – one Swedish commenter who goes by the handle “Jedi Welder” said: “Besides my brain, my entire body is replaced atom by atom every 7 years. Still me though.”

    And that started me – or more accurately, re-started me – down the path of thought I’ve been following intermittently for many years: the riddles of self, identity, consciousness, brain, concepts of “mind” and “soul”. I haven’t chased it through the internet until today however, and it’s obvious there’s a wealth of provocative and enlightening writing out there. There’s also a lot of junk, as you probably know better than I. Have read some Douglas Hofstadter, some Dawkins, and struggled to make sense of Roger Penrose.

    Why the knowledge of atomic/molecular-level of body & brain material replacement is important, is because it lends a sort of legitimacy to a whole gamut of thought experiments, some revolving around a hypothetical perfect “Star Trek transporter”, with the following properties: it can destructively or non-destructively read out the exact pattern of your human body, including of course all brain neurons, interconnects, and the state of every neuron, and then transmit that information to something like a super-duper “3D printer” which builds an exact copy (including neuronal states) of the brain and body. The point here is that, aside from the speed-of-light teleportation aspect, making exact copies of ourselves is already (and always) happening, and at the atomic / molecular level, we are being replicated and very little of what we are now was part of us a decade ago.

    This 3D printer can in fact print out more than one copy, so an individual identity / consciousness can be replicated multiple time (I think there’s a ST-NG episode with replicated Rikers). From the point of view of the copy at the “printer” site, he’s been almost-magically transported at the speed of light from point A to point B. If his predecessor was non-destructively read out, he (the original) finds he’s still in the same old place and he sees his duplicate was created at the printer. If on the other hand he’s been “destructively” read out… well, the original person has in effect been vaporized, atom by atom, and perhaps outgassed as a worthless cloud of organic molecules; can you get any more dead than that? (does it hurt? hard to think of a worse way to go…)

    and so on. I’m beginning to think that consciousness is an illusion, that we imagine perpetual consciousness simply because imagining oblivion is inherently impossible. Lots more to say but I’m new to the discussion and I have a lot to learn first.

    Thanks for posting your thoughtful and creative articles.

    Dick Lawrence

    • stevegrand says:

      Thanks Dick. Exactly! Couldn’t have put it better myself, especially the part about imagining consciousness to be perpetual simply because it’s impossible to imagine our non-existence (despite the fact that we were all non-existent for 15 billion years until we were born!) I think we’ve got our entire understanding of the universe inside-out, really. It’s a creative place, which “invents” new kinds of entities all the time. Many people can’t get past the belief that if something exists today then it must always have existed. Even many physicists seem to suffer from this illusion and often write ridiculous things about how consciousness is some kind of elemental property of matter. Yet matter itself didn’t exist once, and nobody would dispute that matter is a real thing, so there’s no reason why the universe couldn’t have “invented” minds too, once things had cooled down enough to make the complex interactions possible.

  34. Doesn’t seem possible that I will die. I have been with me so long and I feel real, permanent, enduring. It doesn’t seem right that I will disappear forever – I exist right now, I feel so real – just as real as the universe.

    How can I feel so real and yet be disappearing, dying? Maybe that’s because I AM REAL! Maybe I am the only real thing because I AM NOT A PHYSICAL THING.

    Speaking of the physical world Heisenberg said: “There’s nothing there.” Whatever I am, I am not physical. I am not matter – I’m pretty sure at this time, that, whatever I am, I am not the stuff my body is made of

  35. The Second Law of Thermodynamics implies that the universe moves from an ordered state to disorder: sometimes referred to as the “heat death of the universe” A nuclear physicist (I can’t recall his name) once gave a talk about his findings on disordered nuclear states actually being a new form of order and suggested that ordered systems may not deteriorate into disorder but rather change into a different form of order. Could the second law be all wrong and “Order”actually be one of the conserved quantities in nature? That could have implications for the human spirit which seems to me to be a Chaotic “Strange Attractor” and not only an Ordered System but an ultimate “Orderer”. Perhaps death is changing ones state of order.

    • stevegrand says:

      Funnily enough I’ve just been discussing this with someone. The only problem with the Second Law, as far as I can see, is that it’s not a law. It just describes a tendency. Or more accurately it describes the aggregate behavior of a closed system and says nothing about what can happen in localized regions of that system. Organisms are local spots of negative entropy – they use the energy flow around them to construct local order, just like you say. But this isn’t in conflict with the 2nd law. They create and maintain this order by disordering their environment (eating other animals, say). The overall effect is a rise in entropy, even though it decreases quite substantially in local regions. All the interesting stuff in the universe comes into this category – hurricanes, people. Although I agree with what you’re saying, I think order is a bit of a red herring, though. After all, a crystal is far more ordered than a person. I think the best word is organization, which involves increasing order but isn’t the same thing. Here’s a thought experiment: take two Pentium processor chips, cut one in half and rotate one half before welding them back together. One is still a computer chip and the other is now just a piece of dirty silicon. One can do amazing things; the other probably does nothing. And yet they both have virtually identical levels of order, complexity, etc. A person who has just died is almost indistinguishable from how he was a moment before. No special stuff has been lost. He hasn’t got significantly less ordered (although he soon will!). The difference between the two is qualitative, not quantitative. Some kinds of order are more “interesting” than others! Something to chew on, maybe 🙂

  36. Ron Webb says:

    How did I land on your blog post? I’m debating the abortion issue online, and my anti-choice opponent has challenged me to explain why a fetus, a child and an adult are not all the same “entity”, and should not therefore have the same rights. Her premise doesn’t even support the conclusion (even the same entity can have different rights at different times), but I thought I would point out to her that the premise itself is also questionable. I was dimly aware that every atom in our bodies is replaced many times throughout our lives, but it’s just the sort of “factoid” that breeds on the Internet unless we are diligent in checking sources; and so off to Google I went… 🙂

    • stevegrand says:

      Thanks Ron. I’m glad to hear someone’s actually DEBATING abortion instead of just standing on opposite sides of the street screaming at each other! My two-penny’s worth: the only thing that makes me the same person as I was yesterday is that I share the same memories. I lost consciousness overnight and although we talk about “regaining” consciousness that’s pretty misleading – I mean, it didn’t go off somewhere and then come back. Something that wasn’t conscious for hours last night became conscious this morning and he thinks he’s the same person who occupied that body the day before because he has memories of experiencing those things. If someone wiped all my memories and replaced them with someone else’s I’d believe I was that person. Anything that had been done to the previous me wouldn’t have been done to this new person, because he doesn’t remember it. If I had no past, I couldn’t suffer from that past. If I had no sense of the future – no hopes or dreams or expectations or desires – then I couldn’t suffer the loss of that future. I could only suffer in the present moment. A fetus can have little memory of the past and little hope for the future (WE have hopes for it in the future but that’s different). What does it actually mean to suffer in the present moment? We aren’t even aware of the present moment, only the immediate past. Consciousness exists in the past and future more than the infinitesimal present. If an entity has no hopes or expectations that can be dashed, what EXACTLY is our moral obligation to it? Growing up is a gradual process of becoming, and there does come a point where we have to say we’re being cruel to cut its prospects short. It makes no sense to say we’ve reached that point when it’s still a single cell like any other. It does make sense to say we’ve reached that point by adolescence, say. But there’s no meaningful threshold between those two, only a gradual process. It seems to me that abortion is neither right nor wrong – it’s more or less wrong depending on other factors (like the potential suffering of the parents). It would be nice if we could ALL have a grown up philosophical discussion of these complexities instead of being polarized into two camps based on little more than gut feeling, so good luck with the debate! Both of you!

      • Gerard says:

        Hi Steve, in fairness I never thought we’d be discussing the abortion issue here, but hey, why not. I understand the points you made above, but have a few issues with it i the sense that while in a ‘clinical’ sense you are probably correct the whole idea of moral obligation is I believe somewhat missing the point of joint humanity.

        I could say I have no moral obligation to someone I don’t know who falls under a car beside me on the street, since I have no knowledge of their life, or theier dreams, aspirations or potential. Equally I have no moral obligation to people who live on the other side of the world, who I never have nor will meet, and I have no associtation with, The Indian girl raped and murdered in Delhi is an example. So theoretically, to follow your line to it’s logocal conclusion, we end up in in group think is some way, since our lack of moral obligation, derives from our ability to empatise with simialr beings.

        In a geo-political sense that leads us to the dreadful situation where one Israeli is worth 100 Palestinians in some sections of society, based in that case on religion, skin colour and a perceived social and socialtal similarities.

        If you remeber when we originally corresponded it was about my daughter, who was born at 26 weeks and is now a beautiful 21 year old finishing her college degree. She was born at a fetal state, if we let the idea that babies are fetuses until they should be born stand. Another baby was born in the same hospital at the same time at only 22 weeks, and was actually better than my daughter, health wise, sinc ethe doctors knew it was unlikely to go to full term and so had administered drugs to speed up fetal lung development; one of the main problems with premmie babies if the under-developed ling function, making it difficult for them to breathe outside of the womb.

        Here is the problem; in the UK late term abortions are permissable until 24 weeks, at which time my own persoanl experience proves to me that a vialable human is being discarded. This must be morally questionable, and I belive that shared mumanity must make this an ‘appaling vista’ in a legal sense.

        I am not anti abortion in total, I just believe that this is an area where threading should be done as softly as possible, and an upper limit on time of gestation should be applied. In most European countries abortion is available up to circa tweleve weeks, and after that you need a damn good reason!

      • stevegrand says:

        Hi Gerard,

        Oh, but I didn’t make any assertions. I really don’t pretend to know the answers, I only know that we (our species) are not discussing this with anything like enough clarity. I think its one of the shoddiest, least competent debates of all time, and we owe it to everybody concerned to get off our asses and discuss it thoughtfully. My point was only that the underlying issues are not as simple as people paint them.

        > I could say I have no moral obligation to someone I don’t know who falls under a car beside me on the street, since I have no knowledge of their life, or theier dreams, aspirations or potential

        That’s not what I was saying at all, and I’m sorry if it came over that way. I was saying that if the person who falls under that car EXPERIENCES no dreams or aspirations themselves (their potential is a different issue), then what (that’s a question, not an assertion) are our moral obligations to them? It’s a very different thing from whether I’m AWARE of their dreams or aspirations. When it comes down to it, I think the only sensible moral anchor is one based on what we WANT. Do unto others as you would have them do unto you – i.e. what you would want them to do unto you. I don’t want to suffer, and thus I have a responsibility to others not to let them suffer too. Part of the question we should be asking is what does it actually MEAN to suffer, and to what degree can a foetus suffer? Some arguments for the cut-off point are based on when pain neurons begin to fire, but although that’s at least a comparatively intelligent intention, it’s still not thought through, because it’s merely an *assumption* that the functioning of nociceptors marks the transition to the ability to suffer.

        I totally agree with you that there should be an upper limit (or limits) and that limit should probably (why I say “probably” is too complex to discuss in a comment, but it needs to be inserted) be during pregnancy. And like you say, we need a damn good reason. The whole problem is, NONE of the reasons anyone normally states is a good reason. We must do better than this, but there’s no debate, at least here in the US. There’s just rhetoric, and only two positions are being held – they either say abortion is wrong from the moment of conception, or abortion is fine right up to the moment of birth. I think both of those extremes are based on nonsensical arguments and nobody seems to be coming up with better ones.

        I agree that viability and future potential are part of what we have to discuss, and yes, it’s most definitely morally questionable (although the existence of the question does not imply the answer – that would be a logical fallacy), but nobody is asking the right questions! I’m ashamed of my species for the pathetic quality of the debate. I see nothing but people who “feel” what’s right and then try to post-rationalize it. I’m sick of people arguing from the conclusion backwards to the premises in general, quite honestly. When will people ever learn how to THINK? But this is a life or death issue – the lives of the baby, the mother and the father are at stake. It should be a headline issue, based on more than mere dogma and rhetoric, and we need to recognize that most of our innate presuppositions about what it means to be alive and/or conscious are totally wrong and need thinking through far more carefully. It’s the main reason I’ve devoted my life to Artificial Life. There is no room for “beliefs” here. We need logic.

        But anyway, sorry for the confusion.

      • Gerard says:

        Thank you for the long response! In short the lack of thought is a serious problem in this case, to paraflace Richard, people would rather die than think, and they often do.

        Personally I think abortion is a blunt instrument, and it’s original construct was based on morality issues, i.e. oh shit I’m pregnant and going to be ortacised/shunned/hung in the case of Afghanistan ( which in fairness is a really good reason)

        The two extremes, I believe get us towhere, get us nowhere, but we seem to be stuck with them. Not disimilar to the Euro debt debabate in some ways which seems to be playing out as a moral tale of rectitutue versus logic.

  37. Darius Caergrim says:

    I have pondered the idea of non-spiritual reincarnation for some time. The Big Bang demonstrates that our universe began at a definite point in time. This means that a universe can be born. It seems probable that whatever led to the Big Bang could happen again and there have been many theories advanced for what caused it. Assuming that and what is likely an infinite amount of universes, is it not possible for us to be reincarnated non-spiritually when our pattern emerges once more? It wouldn’t be you as you are now. You wouldn’t retain the memories of this life; however, it would be you as you were when your pattern originally emerged. I know you have argued that we are the sum of our memories, but there is still a proto-you that existed as a blank slate ready to form the memories that would now populate our minds. The new you would be as conscious as you are now, but without the same memories. If we were to take this further, we could propose that if all the events that preceded this point in your life occurred again and all that made you who you are now was recreated perfectly, what would be the difference?

    • stevegrand says:

      Good point. Given an infinite number of universes I guess we can be absolutely certain we’d each exist an infinite number of times over! (depending on which kinds of infinity are involved). I’m pretty dubious about multiverses myself, but yes, given that scenario, the same pattern occurring twice must surely be the same person. Of course both would consider themselves unique beings in their own right, and if they happened at different times it wouldn’t feel like one of them had died and then been reincarnated.

      In a pretty real sense, identical twins are already “the same proto-pattern” occurring twice. They’re genetically virtually identical, came from the same womb and lived very similar lives for a while. But they’re confident they’re separate people. Conjoined twins are even more striking in some ways.

      It’s so HARD for us not to assume that minds are little objects that can “neither be created nor destroyed”, don’t you think? If I copied my pattern, memories and all, molecule by molecule, there would be two of me, and each would be convinced that the other was someone else.

      • Darius Caergrim says:

        Thank you for the reply, sir.

        I am not sure I agree with you on this. You have said as much yourself that we are a pattern that is in constant flux between constructive and destructive forces. The matter that constitutes us in a constant state of shifting, changing, and rearranging itself although the pattern persists. Assuming an entirely materialistic perspective of the mind, then it shouldn’t matter if that pattern is broken and reformed. It would still be the same pattern. And there shouldn’t be any difference in your experience. You wouldn’t even notice that the pattern suddenly collapsed and that billions of years have passed since its reformation. I can recognize the paradox that arises with clones, but are we not already an endless series of ‘clones’ that differs slightly with each increment of time?

      • stevegrand says:

        Yes, if what you’re saying is that a second “you” gets created that exactly matches the structure of the first “you”, but after a gap of billions of years, then you’d definitely believe none of those years had passed at all and you were the same person throughout. You’d be pretty boggled by the changes that had occurred around you, but you’d still feel a sense of continuity. Maybe I didn’t explain myself very well.

        We are who we remember ourselves to be – that’s the only thing we can possibly be. So if someone rearranged the neurons in my brain to exactly match the wiring of yours, I’d be you. But a different you. If I made a clever 3D printer that could copy my body, atom for atom, then I could make as many “me’s” as I wanted to. Every single one of them would believe itself to be “me”. I could probably convince them I was the ORIGINAL me but I’d have no other special features than that – we’d all have an equally legitimate right to call ourselves Steve. We’d all remember the same childhood. None of us were there for it, even the first me, but we’d all remember it with equal conviction.

        I don’t think we disagree, do we?

        [Edit] What confused me was this:

        > You wouldn’t retain the memories of this life; however, it would be you as you were when your pattern originally emerged.

        If THAT was the case then the second you would be like your identical twin. It all depends what you mean by the same pattern but without the memories. The memories are PART of the pattern. I thought you were saying the second pattern was a copy of how the first one was BEFORE it had developed any memories. “You as you were when your pattern originally emerged” is a baby. A second copy of you as a baby isn’t really you, because you ARE your memories. It feels to me like you’ve got some lingering dualism there.

      • Darius Caergrim says:

        I agree with what you are saying for the most part, but I think we disagree on the matter of continuity and the original self. A replication of our pattern should materially be no different. The pattern itself has not changed, only the space and time around it. And that extends from any point in my sense of self-continuity. That means I, the original me, should still persist as well because there is no difference to me. So if I should die right now and a replica immediately appear that mirrors me when I was 12-years-old then it should still be me and I should experience the world as I did when I was that age I think suggesting otherwise necessitates that there is more to consciousness than the sum of the matter that creates it, such as dualism.

        At the same time, the clones should also exist and have their own subjective experience as well. So we have two paradoxes here. One in which you can have exact replicas of yourself that have their own sense of self. And the other in which a replica of you should still be the you that is perceived now or at any point in the continuity of consciousness. It is really quite mind-boggling.

        I hope I am articulating myself clearly! 🙂

      • stevegrand says:

        Aha! Then yes, we agree with each other. I’m pretty sure.

        Say three copies of you suddenly emerge a billion years later. One is a copy of your pattern when you’d just been born, one when you were 12 and one as you are now. All three of them would believe that one moment they were in the 21st century and the next moment everything had changed. They’d all perceive continuity of self. One would continue to believe it was the same adult and one would continue to believe it was the same 12 year-old. The only weirdness happens with the baby, since the baby doesn’t really HAVE much in the way of beliefs yet and doesn’t have much of a sense of self that it can feel has continued. To the extent that it’s capable of experiencing it, it will believe it’s the same person and a billion years have passed overnight, just like the others. But since it doesn’t even know what a year is yet, and has very little idea what is normal and what isn’t, and because it doesn’t have much of an autobiography yet, that personal sense of continuity would be pretty weak. It would be the blank slate that you mentioned. The baby is closer in spirit to an identical twin or clone than it is to a reincarnation of you, because it doesn’t really remember existing before now, but it’s just a matter of degree, that’s all. Babies probably feel like that when they wake up each morning. Sort of like sheep, being constantly startled by everything. There’s not really much of a “you” to copy.

        I think we’re on the same wavelength.

      • Darius Caergrim says:

        I appreciate all the great replies, sir! It has been good bantering back and forth with you over this.

        I think we are still off track, my friend. The bone that I have been picking here is your argument that any replica would have a different sense of self. And the reason I have latched onto this is because it is a paradox based upon the arguments you have put forth about consciousness. Allow me to restate my arguments:

        Consciousness arises from a pattern of matter that is itself in a constant state of flux. From one moment to the next, the building blocks of your mind are being rearranged, broken down, or built up. In spite of all this change, you maintain a distinct sense of self. Since your consciousness is only an emergent property of a configuration of matter, then it stands to reason that if it were broken down, scattered all across the galaxy for billions of years, and then somehow reassembled as it was before that it would it be you. I am not talking about someone that talks, looks like, and acts like you. I am talking about the original you. There is no difference. It shouldn’t matter if the continuity were broken. It shouldn’t even matter when the continuity was broken or where it was resumed because at all points in your existence you have been you and that arrangement has been you.

        And let’s assume you died, then in the far flung future your pattern managed to reform itself as proto-you while undergoing the same experiences as you did before, then there wouldn’t be any difference. It isn’t a separate being with its own experiences. The pattern is you and you are the pattern whether here now or there 4 quadrillion years from now. The only way it could not be the original you is if there is more to consciousness than the material world.

        Perhaps consciousness is not so rigid as one might think. Would you argue that someone that experienced brain trauma and significant amnesia is a different being with their own qualia? Would you argue that someone that has died and came back to life to be another being experiencing its own qualia?

        I hope this isn’t boring or aggravating you. I really appreciate being able to bounce these ideas off of someone and receive great arguments in return. By the way, I saw your message asking how people found this particular blog. It was because of this post. I was looking for information to support my thoughts on non-spiritual reincarnation. And one thing I was looking at specifically was matter and how it is constantly changing. You have a great blog here. I’ve already read several posts! =)

      • stevegrand says:

        > Consciousness arises from a pattern of matter that is itself in a constant state of flux. From one moment to the next, the building blocks of your mind are being rearranged, broken down, or built up. In spite of all this change, you maintain a distinct sense of self.


        > Since your consciousness is only an emergent property of a configuration of matter, then it stands to reason that if it were broken down, scattered all across the galaxy for billions of years, and then somehow reassembled as it was before that it would it be you.


        > I am not talking about someone that talks, looks like, and acts like you. I am talking about the original you. There is no difference. It shouldn’t matter if the continuity were broken.

        Wait, no! There is indeed no difference, but you’re using “original” in two different ways at once. That can be a bit dangerous.

        If I record the locations and momentums of every atom in my body, and a cunning machine moves some other atoms around until they’re in exactly the same relationship as mine are now, there will be another me. I am definitely the original, in the usual sense of the term – I came first, and he is a later copy. But he’s just as much me as I am – I’m only the original in historical terms and don’t have any special ontological status because of it.

        Whereas if I recorded the locations and momentums of all my atoms and then I was dissipated – scattered, as you put it, I would be dead. If someone else came along later and used the information I’d recorded to move atoms around and create a copy, that would be a real me again and I would be delighted to have been reincarnated, but its not the “original” me in the normal sense of the term.

        The difference can be seen by assuming the person who made the copy made two at once. You can’t have two originals. It’s probably just semantics, but you seem to be invoking some kind of conservation of souls. I’m not saying these clones merely look like or act like you – they’re both REALLY you in every respect. But there are two of you now and neither is the original.

        Come to that, I’m not the original me either. It’s a meaningless concept. Yes, you can be reincarnated, and you can be duplicated – all of them are you, but you can’t talk about the original you. It has no meaning beyond being a statement about which was the first instantiation of that pattern.

      • Darius Caergrim says:

        We are perfectly aligned then, my friend! It has been a most interesting little debate. =)

      • stevegrand says:

        Ditto. I’ll see at least one of you in some universe some day. Or at least, one of me will! 🙂

  38. Sarah says:

    Hi Steve, Thank you for a very interesting artical. Sorry if this sounds a bit unintelligent but what I am struggling to understand is if all we are is this body made up of atoms and these atoms are ever changing then how do we remember anything from the past? If the atoms in my brain have changed over how many times then surely so has my brain changed and so how do I still remember what I did last year or the year before. I am fascinated in science but also in the idea that we do live on past this life. I was wondering if you have ever found any interest to study the accounts of past life memories, obe’s and such.
    Thanks again though for a very interesting article.

    • stevegrand says:

      Hi Sarah, that’s a good question and not dumb at all. I think the main reason it’s hard to figure out is that we’ve got everything ELSE wrong! 🙂 We’re so used to the idea that a thing now is the same thing it was a little while ago. And yet I don’t think that’s really true about anything. My Granddad used to say “I’ve had this hammer all my life. Of course, it’s had two new heads and three new handles since then, but it’s the same hammer.” I think that’s the answer to your question – in some ways it IS the same hammer. It wouldn’t be the same hammer if you replaced the head and the handle at the SAME time, but if only one part gets replaced at a time then it makes some sense to say it’s still the same hammer. If you see what I mean!

      So in terms of the brain, memories are the connections between neurons and the ways that those connections influence signals that pass across them. So what makes you into “you” is the “wiring diagram” of your brain. When the atoms in a neuron get replaced, they don’t all get changed at once. First a head gets swapped, then a handle. The atoms that remain are still able to function as a complete cell in the mean time and maintain the structure of the wiring. It’s also possible that a whole neuron might die, and if each individual memory was stored in the wiring of a single cell then each neuron that dies would wipe out an entire memory, but the evidence suggests that memories are actually stored holistically – rather like the image in a hologram. So it’s possible for one cell to die without having a noticeable effect on the memory, because that memory relies on many thousands or millions of cells. And then perhaps another cell can grow and sort of copy everybody else, growing connections that roughly match those that were lost by the dead cell.

      Imagine you had a room filled with people, and every person knew just one word from a story. Imagine that there are enough people so that several of them know the same word. If everyone shouts their word in the right order you can reconstruct the whole story. Now imagine people leave the room occasionally. If everyone who knows word number 53 leaves at once you’re in trouble, but it’s not a problem if only one of them goes – you still have the story. Now imagine new people are entering the room at about the same rate as people are leaving. Suppose they wander around and if they hear a word they like, they remember it. Now it really doesn’t matter if one of the word-53 people leaves, because some others still remain and a new person may come along later and also learn word 53 from them. The story never dies, even if you end up with a completely different set of people than when you started!

      [Er, which is pretty much what you said in your second comment!]

      Transporters are fascinating. They’d HAVE to be good enough to copy the fine details of the wiring of the brain, so the memories would travel too, but like you say, what you’d get is a copy. You would step into the machine, it would make a noise, and then nothing would seem to have happened – you’d still be there. But meanwhile, on another planet, a DIFFERENT you would be quite certain you’d stepped into the machine and been transported to this new place. Now there are two of you!

  39. Sarah says:

    I think I have just answered my own question the atoms are contained in the cells and since the atoms are not changing all at the same time the memories are retained. I guess if I am right with this it kind of rules out the possibility of star treck style teleporter working as the new copy would surely not hold any of the former memories. (I think :-D)

  40. Gh0$T v1rU$ says:

    Hi mate, great article although, I feel compelled to point out the fallacy of your reasoning as regards to personal identity in the comments. I noticed that you claim our memories are what gives us the continuity, the very fact that we can remember yesterday would suggest that we are one and the same person over time. To this we attribute the psychological continuity of our selves existing over time, since we cannot attribute this continuity to the physical body.

    However, this is not accurate and was dispensed with nearly 400 years ago in the tomes of philosophy. John Locke suggested that it was the continuity of consciousness tied together by our memories which was requisite for identity over time. However this falls foul of ‘Thomas Reid’s fallacy’ (check out wikipedia) which leads us to an ad absurdum. Furthermore, the consequence of this line of reasoning becomes apparent when we consider Hume’s refutation which is simply if you cannot remember what you were doing three weeks ago on Tuesday, then you are not the same person. Again, sticking to the absurdity of memory as consisting of our identity, has been demonstrated to be logically impossible.

    I am actually writing an article on pointing out the fallacies of our notion of identity because as recent theory suggests, the self is an illusion which means that “you” as an agent of volition has no independent existence as an entity, rather like the Bhuddist conception of ‘Anatta’.

    I enjoyed your article and it was useful to find out that there were radioactive isotope studies completed, that demonstrated this principle. It was also interesting to find out that it has not been established conclusively, since some molecules may remain (ref: comment on pharmacology studies).

    • Darius Caergrim says:

      I agree with the gist of what you are saying here The core of our consciousness, the qualia so to speak, is separate from our identity. Our memories may form the foundation of our self-identity, but our identity is not our consciousness. It is a separate issue altogether.

      • stevegrand says:

        It seems to me that “identity” is not a possession; it’s an ascription. I ascribe a certain identity to something or somebody; they don’t possess it. If my hammer has had two new heads and three new handles, is it the same hammer? Well yes or no, according to what you want the question to mean. There’s no point asking whether it IS the same hammer, only whether we can reasonably CLAIM it’s the same hammer. It’s like asking whether something is alive or not – objects don’t carry little union cards around with them to say if they’re REALLY alive; life is an imposed category, and it’s up to us to ask whether it makes SENSE to regard something as alive or not. There’s no such category in Nature. Same with identity. The universe is just what it is. Ideas like “sameness” and “identity” are descriptions we apply to it, not facts about the universe itself.

      • Darius Caergrim says:

        Perhaps so, sir!

        I have attempted to hedge all of my bets here by considering all perspectives of consciousness, whether material or metaphysical. If I am merely an organic machine, then so be it. If I am more than that, so be it. I perceive a sense of self regardless of the mental gymnastics involved in establishing identity, consciousness, or whatever. There is certainly a Darius in my mind and in yours just as there is a Steve Grand in my mind these days.

      • stevegrand says:

        Haha! Taking Pascal’s Wager, eh? 🙂 I personally think physics and metaphysics aren’t as separated as we historically thought – they’re both equally wrong and there’s a Third Way that we haven’t quite figured out yet. So maybe you can have your cake and eat it. Organic machines we may be, but there’s nothing “mere” about them at all. The universe is an endlessly creative place and I see no upper limit to how sophisticated machines can be or how many levels of emergence can arise from mechanical processes. A Darius there is, and a Steve too. We’re just not nearly as unitary and discrete as we tend to think. It’s like a hurricane – it’s a real thing but where exactly is the edge of it? Boundaries are things we apply to the world, but the world has no boundaries – it’s just a “general sort of mish-mash” as an old friend used to call it. To quote the Bible: “My name is Legion, for I am many”!

    • stevegrand says:

      Ha! People don’t often accuse me of logical fallacies and I don’t often fall foul of them, so I’m up for a bit of cut and thrust about it! 🙂

      You seem to be making the presumption that I believe in continuity of self any more than you do. There needs to be a better word than “illusion”, because that implies a subject to be illuded, which is pretty recursive in itself and often begs the question. But I don’t believe there is a “self” in any kind of unitary way at all. At best I’m only the story I tell myself, and in this instance recursion is not only permissible, it’s essential!

      > if you cannot remember what you were doing three weeks ago on Tuesday, then you are not the same person.

      Well who said I am? I certainly don’t. I’m not the same person from moment to moment. My entire attitude to life seems different today than it was yesterday (according to those autobiographical memories that come to mind). I’m constantly deluded, frequently plural, largely unconscious of my own intentions and actions, and I claim no more right to my own existence than “America” can claim for itself.

      What you may not know is that I make brains for a living. These are fully distributed systems – there is no homunculus, and the part that (will eventually) tell us that it “exists, therefore it is,” is merely the collection of parts connected to the mouth. Many other awarenesses of equal ontology exist in the system, but they can’t report their existence directly. All of these parts have memories of their own (memory being fully distributed too) and EXHIBIT continuity as a result. But it’s pretty much meaningless to ask whether they’re ACTUALLY the same entities they were a few moments earlier. They would tell me they were, if they could, but that means no more than me telling you I’m the same person who used to have curly hair and liked playing cowboys and injuns on my tricycle.

      The entire universe consists only of continuity of pattern, and then not continuity of the SAME pattern, only continuity of change. This applies to electrons as much as to minds. Locke was born a few miles from me, but a lot has changed since his time, so I don’t have much truck with any “it was disproven centuries ago” arguments, because Locke & Co. weren’t party to the things we know now about neuroscience and emergence. Logic is only as good as its axioms. Including Buddhist logic, although I have a lot of sympathy with Buddhist ideas.

      But it sounds on first glance like I’m just as dubious of the existence of a self as you are, doesn’t it? I’d be interested to read your article, if I may.

  41. Gh0$T v1rU$ says:

    Hi Steve, yes I did make that assumption based on your comments here, it seems clear that you have considered this so my accusing you of a logical fallacy was unwarranted since I was only going off a couple of the comments here. I certainly don’t like to stand behind ‘it was proven centuies ago arguments’, however, it has been demonstrated that the continutity of consciousness tied together by memory is insufficient to provide continuity of identity.
    It does seem to me that we are of the same opinion here, in particular the view that there is no centre of experience, or a cartesian theater for a homonculus etc… The fact that the brain is a fully distributable system and is constantly changing does lead to the fact that questions about being the same ‘thing’ over time are redundant particularly when we are talking about “us” being the physical matter itself that constitutes the brain and body.

    I take Dr Metzinger’s self model theory to be the best explanation for the brain mapping an artificial self model over reality that provides a structural requirement for a brain to have advanced cognitive capabilities. As you say, the notion of self hood is simply the story that is believed to be about you. Can you point to some of your posts on emergence, do you lend support to a weak or strong emergent position just out of interest?

    Many thanks, I’ll send you a link when I finish it 🙂

    • stevegrand says:

      Phew, that’s a relief. I don’t mind being wrong but I hate being illogical! 🙂

      I think the crux of the problem in this area is the ease by which linguistics confuses levels of description, don’t you? On one level it’s quite reasonable to say I’m the same person as I was years ago and have an independent existence, and on another it’s not. Same with free will – on one level the concept is meaningless and any attempt to define it obliterates it, while on another level it’s a very useful construct with real meaning (albeit not the meaning most people assume).

      I take a strong stance on emergence but I don’t define it the same way as most people do. There are hints here and there under the Emergence menu on this blog (e.g. https://stevegrand.wordpress.com/2009/06/15/between-a-rock-and-a-hard-place/), but I also wrote a book that was based on my perspective, even if it didn’t do it justice (Creation: life and how to make it). I have another book called Spirit in my head, but it won’t come out on paper yet 😦

      To me, emergence is a concept that should properly be applied to “phenomena”, and the criterion for being a phenomenon is that it’s a repeatable and PERSISTENT juxtaposition of causal connections. In my view, an electron is an emergent phenomenon in the substrate of fields, in a roughly analogous way to the way ripples and vortices are emergent phenomena on the substrate of water. Those two are the only known self-preserving forms on that medium (although there are more if the water is moving or constrained). Once upon a time there were only fields (whatever they are), but those fields got disturbed in a variety of ways, most of which dissipated while a few remained because they were stable. Those disturbances stayed around long enough to be given names (photon, proton…), and together constitute a new level of description – a new level of BEING. The universe invented something new. And once a new level of being comes into existence, it permits new kinds of meta-disturbance in which other forms are self-preserving and even more levels of being can emerge. So until there were particles there could be no atoms, but once there were atoms there could be molecules and chemistry, and once there was chemistry there could be life. At each level, new mechanisms for self-preservation come into play. Photons maintain their form by constantly “running forward to avoid falling over”, whereas the autocatalytic networks of chemical reactions that we call creatures maintain their form through metabolism, adaptation and reproduction.

      So on that basis a mind – a person – can be looked at as an emergent phenomenon, whose persistence is brought about through prediction, simulation and reflective self-reference circuits (forms) within the substrate of populations of neurons. But since we are minds ourselves, we tend to get mixed up about whether we’re looking at them from below (as a neuroscientist would) or sideways from the same level of description. Philosophers try to look at them from above, but that’s fraught with difficulties because they’re conceptually above eye level. Above minds there are other levels, like mobs and societies, and we play mindless parts in these, just as neurons come together to make us without knowing that their own self-preserving, symbiotic processes form part of something bigger and real in its own right.

      I see the entire universe as being a hierarchy of forms – of recursive relationships. They’re pretty fuzzy round the edges and we often impose more order on them than they deserve, but they are real things, by virtue of their recurrence and stability. Minds are just as real as matter, as long as you look at them from the right height. From lower down, they’re shifting, plural, decentralized eddies in nerve activity (in much the same way an electron ceases to be a “thing” when you look at it from the perspective of fields). Hope that makes sense – it really does need a book!

      Look forward to seeing your article.

  42. Gh0$T v1rU$ says:

    Hi Steve, I certainly agree with you on the confusion that language generates, and I am also glad to see we have a similar take on free will too. These things as concepts are essential to us, so there is a level where they are valid in communicating with each other, even if these concepts are not what people really think they are.
    I would not disagree with your emergence of phenomena idea, although I am not sure I like the idea of allowing property dualists to have room to maneuver, particularly as it is an empty doctrine with regards to having an ontology of non-physical phenomena. I am not sure if you support that position as a ‘qualia freak’ or not, I will have to read one of your books!
    Thanks for taking the time to explain your position, I look forward to dropping by again 🙂

  43. Pingback: The Cynical Optimist » Blog Archive » We Never Died

  44. Dana says:

    In answer to your question about why I googled to find an answer to how often my body’s “stuff” is replaced, it’s a symbolic thing. I’m looking to make some personal changes in my life, and it’s encouraging to think that if I succeed then a year later the man I was will only be 2% there, even if in a more realistic point of view the me I want to be will be much the same, right down to scars on my hands and feet from needle pricks in my first days after birth.

    • stevegrand says:

      That’s a nice answer. Someone earlier wanted to know that the bad things that had happened to her in her past would once day be sort of washed away. I think symbols like that are important. Being such dynamic systems we can simultaneously remain the same and yet change, like a Shinto shrine that’s still the same shrine even if it’s a new building. Thanks for letting me know, and I wish you the best for the transformation! I’ve been there myself.

  45. Claire says:

    I first read about “body recycling” in Richard Dawkin’s The God Delusion (someone earlier said Dawkins quoted you but I don’t remember). I’m now reading your book Creation and there it was again. You’re right, it does make the hair on the back of my neck stand up! I googled “how many times atoms in body replaced” and your blog came up.

    Question: Re your statement that an atom(s) that was in my body on the day I was born is statistically likely to be back in my body at some future time…aren’t there just too many atoms for this to be statistically likely? I can understand a different atom, but the same atom?

    Also, I’ve heard that individual water molecules in an ocean wave stay static, while the wave moves “through” them. How is this different (or is it?) from the air molecules moving along with the wind to form an orographic cloud? In other words, the air molecules move with the “air wave” whereas the water molecules remain stationary with the “water wave”?

    • stevegrand says:

      Thanks Claire! I’m glad you’re enjoying my book. Some people get it and some don’t, but I’m only really interested in those whose minds work in such a way that they do 🙂

      Haha! So my words have passed through your mind three times already! What are the chances of that happening? 🙂

      I may be wrong about the chances of one of your atoms being back for a second time, although others have suggested that every glass of water you drink is quite likely to contain at least one molecule formerly excreted by Isaac Newton, and if that’s true then the chances of there being one formerly excreted by you is basically the same. Probability isn’t my strong point, to say the least, and although there are many ways to work it out, they all involve a lot of big assumptions and unknowns, so I get a different answer every time and can’t swear to it being a fact. But probabilities are very counterintuitive things in exactly that sort of way. Your birthday is only one out of 365 possible dates, yet in a room with only 23 people in it there’s a better than 50:50 chance that two of them will share a birthday. That’s not a very good answer, I’m afraid. I really should sit down and work it out carefully, but there’s not space here. I’ll try to get round to it when my head’s not full of code and maybe write a post about it.

      > In other words, the air molecules move with the “air wave” whereas the water molecules remain stationary with the “water wave”?

      That’s a very good question. Water molecules in an ocean wave do move, but mostly just up and down (in an ellipse, strictly). Perhaps the two things don’t seem so different when you recognize that movement is always relative to something – there’s no such thing as absolute motion. A water wave moves over a “static” ocean and a wave cloud stays “static” while the air moves through it, but these are basically the same thing seen from different perspectives. When you try to understand how an aircraft wing works, it doesn’t really matter whether you think of the wing as moving through still air, or air moving across a still wing. If you imagine yourself in a balloon, floating along with the wind, you don’t feel a breeze because you and the air are moving together. If you don’t look down, you have no reason to believe that you’re moving at all. And if your balloon then passes through a region of orographic cloud and you can’t see the ground or the mountain at the time to act as a reference point, it seems to you as if the cloud has rushed towards you and swept over you. Only someone standing on the mountain would say that you and the balloon were moving while the cloud stayed still. And even if you do see the ground, it has no more right to be considered stationary than the air does – after all, it’s traveling at thousands of miles an hour round the solar system, which is traveling at thousands of miles an hour through the galaxy… Does that answer your question or am I missing something deeper?

      P.S. If you look at photos of fast jet aircraft, you sometimes see “orographic” cloud produced from water vapor as the air is disturbed by the wing. This cloud moves along with the plane, always staying just behind the wing, but it’s essentially the same process. The plane is just acting like the mountain, except that from our reference point planes move and mountains don’t.

      • Claire says:

        You answered all my questions perfectly and thank you for the quick reply! Keep writing! Your sense of awe comes through in your words and your ablility to explain difficult concepts is great. I’ve always been awed by life too…I used to wake up in the middle of the night just astounded that “I” existed 🙂
        Thank you again!

  46. Cyd Ropp says:

    Answering your question regarding “why Google this?”, I was actually wondering if the atoms within our bodies need to transport in and out of the body when they’re “turning over,” or if they could instantiate in place right out of the quantum foam. Basically I’m wondering if atoms are only generated within stars, or if they can generate directly from the field.

    • stevegrand says:

      Interesting question. As I understand it (although I’m not a physicist), the virtual particles in the quantum foam aren’t the right kinds for making nuclei and matter only forms in stars as you say (the heavier elements), as well as during the early universe (the light ones). And unless they’re radioactive, nuclei are highly stable and hang around for billions of years. But there may be a sense in which nuclei are no more the same thing from moment to moment than a tornado is made from the same air from moment to moment. And even a sense in which the quantum foam produces some of matter’s properties (and what is a thing anyway, if it isn’t its properties?) Physics is starting to look at things this way, here and there. There are hints that particles are really stable configurations of fields, rather than little lumps superimposed on space. Sadly, I don’t think any of that counts for much inside the body – we just excrete broken down stuff and eat more to replace it! It all happens at the ion level.
      This is clearly a big subject for a lot of reasons! I really must write a book about it, because I think it leads to lots of interesting new ways to look at things. Thanks for the feedback.

      • Matt Griffith says:

        Yes, I’d like to see an Emergence book written by Steve Grand. Can I pre-order? 😉
        One of my favorite books on this subject, besides your book Creation, is http://www.amazon.com/The-Emergence-Everything-Became-Complex/dp/0195173317
        To look at the periodic table as the emergence of complexity of atomic particles is, I think, the right way to go about it!

      • stevegrand says:

        Hey Matt! Sure thing. I just have that little matter of artificial life to sort out first, then I’m onto it. I’d like to write a book called Spirit – based on that very topic. I hadn’t seen the book you mention, though – maybe Morowitz beat me to it!

      • Matt Griffith says:

        Oh that! Right right! 😉

        Yeah it’s a good book. I like to go back to it and read over time to see how my thoughts about complexity and emergence have changed (if any). Definitely a recommended read, though he does a lot of hand waving throughout it. At least you explain subjects with examples!

  47. Hi Steve. I arrived here from Googling ‘particles in humans change every seven years’. I’m studying a bit of philosophy in retirement and trying to get to grips with, in this case, ‘causal determinism’ which lots of people seem to shorten to just ‘determinism’, and how that relates to the supposed behaviour of atoms. The case for determinism is often built on what people call ‘natural law’, which in turn some people reduce to something about atoms. Determinists seem to have a causal theory of how atoms behave; they divide events into caused or random; they then arrive at the notion that given a world state of affairs at time t1, there will only be one state of affairs at time t2. Now, I feel a strong instinct against this argument. It seems to become preposterous when it includes my writing this email comment (as if I didn’t decide to do so, it was determined), and it seems to become preposterous because it seems to trace every event around me back to primal events, and claims to be absolutely right about this, without there being the simplest of models to show the causation behind the tiniest event, like why a neighbourhood crow just landed on the roof outside my study then flew away 🙂

    Well, that’s the speculation that brought me here. But let me while I’m here compliment you on your unfailing courtesy and thoughtfulness in responding to people who comment.

    • stevegrand says:

      Hi Alan, that’s an extremely interesting topic! I can offer you my take on it if you’re interested, but I appreciate that few will find it an emotionally satisfying one.

      I think it partly comes down to the distinction between determined and determinable. Laplace thought that if we could know the trajectories of every particle, we could know the inevitable future of the universe. But in the past 20 years we’ve discovered that even in a completely deterministic system with absolutely no randomness (not that the idea of randomness makes any sense anyway), chaos reigns and unpredictability very rapidly takes over from predictability (due to “sensitive dependence on initial conditions”). The future is determined, in the sense of being a lawful consequence of the situation, and yet it’s undeterminable to anyone studying it. So it’s fairly easy to show that nobody, even in principle, can know what the future holds. The probability that they are right falls to zero very quickly, and the larger the system the faster it falls. There’s also the question of how anyone can be inside that system and think about its future without either those thoughts changing the system of which they are part (hence immediately rendering their prediction incorrect), or without those thoughts themselves being an inevitable consequence of the observations they are making about the rest of the system. And the idea of being somehow outside of the universe, merely measuring things, doesn’t work either, as Heisenberg pointed out. Measurement alters the thing being measured.

      So we have a situation in which the future may well be totally inevitable and deterministic but it’s still completely impossible to know what that future is. Which leads us to ask what meaningful distinction there can thus be between “undecided” and “unknowable.” I’m unable to find one. It’s a distinction without a difference. Remember I’m not just talking about it being unknown through ignorance – it cannot possibly be known. From my personal perspective, I don’t care whether my future is already certain to work out in one particular way (I’ll come back to that), since I don’t know which way that will be, and nor do you and nor can any god. It’s thus still a mystery and I still look forward to finding out what happens!

      If the distinction between undecided and unknowable is meaningless (and I have to leave you to do the philosophy there or else this will turn into a book) then the meaning of “possibility” comes into question too. We can believe, if we like, that the future is undetermined – that anything is possible. But when it comes down to it, only one set of events actually ever DOES happen, so in what sense were the other things possibilities? They didn’t happen. We can say “well they COULD have happened” until we’re blue in the face, but the fact is they didn’t. So what does it REALLY mean to say they could have done? We can’t replay the situation to see if something else happens this time, because you can’t wind back time. We could replay essentially similar situations but chaos theory already tells us that in a deterministic system we may get radically different results each time, not because of any acausal effects but because it’s theoretically impossible to set up the second run the same as the first with infinite precision. So in practical terms what actually happened was what was going to happen and we can’t prove otherwise. Just because we could conceive of other possibilities doesn’t mean they actually existed. It’s in the nature of possibility that it doesn’t actually exist, for then it loses that very property of only being a possibility…

      The get-out from all this semantics is the observation that we operate on many levels of description. At the physical level the future may be quite certain, but nobody can show in advance what it will consist of, so it’s indistinguishable from one that isn’t yet decided (whatever that’s supposed to mean – try defining it and it rapidly vaporizes!) But at the everyday level, terms like free will still make some sense and are very useful, as long as we come to recognize that they mean what we “choose” them to mean – they have no absolute meaning. Without a concept of free will we can’t logically have a concept of justice, and without a concept of justice we inevitably perish. Those societies that happen to develop a sense of justice and therefore culpability will survive more often than those that don’t, and we can hope that we are one of the former. But we have to “decide” what we are going to mean by culpable, which is a whole other topic!

      As for demonstrating causality I think chaos theory already shows why we can’t explain why a crow landed on your roof. But we can dissect the problem down to smaller steps and INFER from their utter regularity that each step is lawful (all reasoning comes down to induction at some level). Raise the temperature of ice and find a circumstance in which, all other factors being equal, the ice doesn’t melt, and then this causal relationship comes under question. But every time we try, either it happens or we find some reason why it didn’t. Philosophically, things can either happen for a reason or they can happen for no reason – there aren’t any other possibilities. Neither gives us much room for “choice.” Say there’s a supernatural god. If he doesn’t interfere with the universe then it’s questionable what we would mean by saying he exists at all, but suppose he CAN interfere. He can only do so by bending or breaking the “laws” (observed regularities) of physics. But we can ask under what circumstances he can break them. Does he break them for no reason? If so then he’s acting randomly and can’t be considered an intelligent being; if he breaks them for a reason, he’s acting lawfully and is just as subject to causality as anything else. If you can usefully ask WHY God did something then his action must have been causally connected to something that preceded it. Again, we can say “well he CHOSE to react in that way” but it begs exactly the same questions we’ve just been discussing!

      So anyway, I haven’t been able to find any meaningful alternative to the dichotomy of “caused” or “uncaused”, and so my actions must either be inevitable or meaningless (meaning being the answer to the question “why?”). But it really doesn’t bother me. I still look forward to finding how things will turn out and whether the things that feel to me like decisions work out to be good ones or bad ones. I’m willing to take part in that giant dance and be glad to have watched it unfold. I can ask no more from life. 🙂

  48. One would think by now, that with all the combined years of knowledge on just about every subject and topic known to man, that would number into the millions and with some topics/subjects, billions of years.
    Man would somehow be a lot further in it’s progress (and I mean “man”, not technology advancement) of understanding man’s inner consciousness.
    But the way humans are taught, with the principle of “remember and repeat”, how would humans truly know what one truly is?
    Perhaps if humans were taught to “think and know”, things today maybe quite different.
    Has any scientist actually monitored an atom from “birth” ?
    Or can’t they as all the universe’s atoms (Adam’s) supposedly already exist and continue to “morph”.
    Because “man’s laws” (physic’s) apply only to man on “man’s earth”, if one was to apply “man’s laws” to the universe, it would not last a nano-second.
    All formulas are man made algorithms, so all life and half lives are usually programmed to reflect man’s theories.
    Everything in known creation formed itself (even the first man: atom/Adam) without the input of scientist’s theories (physic’s).
    A.E.I.O.U, Absolute Energy = Input, Output, Utilization.
    One of anything (even “nothing”) is the I.O.U of AE, as is the next one.
    So how can anyone truly believe what “man” has theorized, when universal/nature’s law doesn’t follow/adhere to man’s theories?

    • stevegrand says:

      > So how can anyone truly believe what “man” has theorized, when universal/nature’s law doesn’t follow/adhere to man’s theories?

      I don’t really know what you’re trying to say, but somebody has clearly lied to you badly about what a theory is. Non-scientists may use the word theory in the same way they use the word “hunch” or “opinion”, but that’s not AT ALL what the word means in science. If nature doesn’t adhere to a theory then it’s simply not a theory, by definition! A scientific theory has to do three things: 1) It has to fit the facts, so if it doesn’t fit the facts then it can’t be a theory. 2) It has to provide an explanation for those facts in terms of other already established facts and theories. 3) It has to make testable predictions. The theory of evolution by natural selection, for instance, is supported by literally millions of facts, explains a huge number of otherwise puzzling things, and has made many testable predictions which have all so far proved to be true. The idea that there was such a thing as a “first man” called Adam is only attested by one fact – the account in the book of Genesis – which is no more than hearsay. It doesn’t fit with a vast number of other facts from the fossil record, from anatomy, from genetics, etc., etc. It doesn’t as far as I know make any testable predictions and it doesn’t really explain anything. So creation is not a theory. You’ll need to explain to me precisely WHICH scientific theories Nature’s law doesn’t adhere to, before I could possibly answer your question, unless it was rhetorical.

  49. unkleE says:

    Hi Steve, remember me? How are you going?

    I don’t know if you are still interested in the question you asked (” If you came across this post by Googling to find out how many of our bodies’ atoms are replaced each year, would you drop me a comment and tell me WHY?”) but I thought I’d say g’day and answer it for you.

    I follow your blog (whenever you actually post!) but I came across this post while searching for the answer to a simple question: are brain atoms replaced over time?. This post came up in 3rd place on Google Search, and so of course i had to check it out. My experience with Google is that Google ranking can be fairly arbitrary, and can depend on whether the searcher has been to the website previously, as I have here.

    Best wishes to you.

  50. Pingback: Death Revolution | revolutionindeath

  51. robby says:

    I googled “how many of the atoms in your body are the same” to try to come across an answer to what I was pondering. I was thinking about skin cells specifically, then it got me to thinking about blood cells and brain cells and bone cells and I got to wondering if 50 years from now I will be made up of completely different atoms than I am now, and if it does completely change how quickly? I will still be the same person but I will not have the same atoms making up my structure. Pretty weird the think about. I really enjoyed the article, good information, good read.

  52. aaronjquigley says:

    I came here off the back of a search when I saw this “fact” in a tweet. I was intrigued by the idea. I’m a CS Professor so the biology and process which would make this happen are unknown to me.


    • stevegrand says:

      Thanks Aaron. If you follow this line of thinking into CS it can lead to some subtle but interesting shifts of perspective around the idea of data-driven object orientation (as opposed to code-driven). Not much use for HCI, probably (although Jeff Bezos apparently based Amazon Web Services around some of my ideas) but it keeps me happily occupied creating a-life simulations, anyway 🙂

  53. Jason Clarke says:

    I came here after viewing Richard Dawkins’ TED talk in which you are mentioned and shown, enviably, in a photo with Douglas Adams. I’m not sure if it will make you feel better or worse, but I googled “Cromwell’s bladder” first.

  54. Miri says:

    I usually never leave a comment, but I saw your “WHY” and the answer is: The teleportation paradox! Would a teleported version of me still be me? I listened to the latest Skeptic’s Guide to the Universe, where they had a brief and slightly heated debate over the subject and got curious 😉

  55. matt burns says:

    Reason I’m here: I wanted to settle an argument with my girlfriend about whether we still have any of the same atoms we were born with. Bone and teeth seemed to be the main arguing points.

  56. I do have questions. I’m only here because it’s a curious subject and it is interesting to me. There are things like sandbars that I imagine are somewhat permanent but where every grain of sand is replaced on a regular basis. It would be interesting to think of a human in the same terms but there are a few questions that come up, like cataracts and other wear and tear, if our bodies were so active in replacing cells it seems like our cartilage and other difficult to heal parts wouldn’t be so difficult to heal.

    • stevegrand says:

      That’s a really good question. I think the answer lies in how we get this structure in the first place. We’re basically tree structures. One single cell divides into two virtually identical ones, then four and so on, but after a short while different cells switch on and off different genes, so that the ones at one end start to divide into something slightly different from the ones at the other. From each of these types some more types arise, but there are only certain pathways available from any node. The ones that can divide to become various other kinds of cell are called stem cells, of course, but eventually we end up with hundreds of different cell types, the vast majority of which can only divide to become cells of the same type. So you have a limitation there on what kinds of tissue can regenerate (hence the interest in stem cell research as a way to “back-peddle” the differentiation tree and re-start a new branch.

      At the same time, the way these dividing cells become arranged depends on a still poorly understood collection of clever tricks – scaffolding, chemical gradients, etc. So building an organism in the first place relies very much on the order in which things happen – the scaffolding has to be in place but can later disappear or go on to perform a different function. Later wounds often can’t go back to the point at which there is scaffolding available to help organize the shape and structure of regenerating tissue, so although we might be able to create new material it doesn’t necessarily end up in the precise and complex arrangement it was in before the damage. Salamanders can regenerate whole limbs, but I guess there’s an evolutionary cost as well as a benefit in leaving tissues in a state where they can go back and start again. Our blood is highly regenerative, our brains remain pretty plastic, but some tissues, like the retina or cornea, probably “can’t afford” the capacity for repair without it getting in the way of their function. The cornea has no blood vessels, for instance, and has to rely on diffusion. That enables the cells to dynamically maintain their internal structure but it’s easy to imagine how having cell turnover in something that’s meant to stay optically consistent might be tricky.

      So I expect the answers are many and various, but the way our cell types differentiate as the body grows, and the availability of the scaffolding that created the initial structure, must be big influences. Imagine a bacterium that divides into two, then four, etc. The cells happen to be sticky and remain glued together instead of swimming off into the sunset. Once the sticky ball of cells has grown to a certain size, the ones on the inside experience a different environment to those on the outside, and so evolution enabled this species of bacterium to switch on different genes in different conditions. Thus the ones on the inside can continue to live and divide, rather than being smothered by the ones on the outside taking away their nutrients. In fact the waste products from the cells on the outside get used by the cells on the inside, and so the whole colony of bacteria has the capacity to work as a team. Some cells might retain the ability to move, while others focus on fighting invaders. Over millions of years this species of bacteria develops more and more ability to differentiate and specialize. Some parts end up “designed” to be sacrificial – they might consume invading bacteria and die in the process. Some become so specialized that they would be totally useless in the wild and depend entirely on the rest of the colony to support them while they do their thing. They might lose the ability to divide. Some might even lose their nuclei, focusing on the transport of oxygen around the colony in return for having their own nutrients supplied from the outside instead of using genes to construct proteins… What you’re now looking at is not just a colony of bacteria but a multicellular organism, like you! If you can get your head around that (and it goes against everything we intuit about ourselves) then it’s easier to see why this unfolding story only has certain endings available to it, even though it is constantly churning matter and energy through itself.

      Hope that helps.

  57. Gregory Owens Duncan says:

    I found your article on Google trying to research a metaphysics hypotheses found on Facebook about soulmates. It stated that soulmates are atoms attraction to each other finding their way back together. I was skeptical and had never spent much time thinking about wither any atoms are actually retained by the body to begin with.

  58. Chee Wai Lee says:

    The thought was originally triggered by Richard Dawkins’ about atoms flowing from place to place. So I wondered if anyone had given any deep thought about how many of my “original” atoms (say at birth … I didn’t want to go all the way back to a fertilized egg) were retained after 42 years alive. As to why your blog post – Google ranked it up at the top, nothing else further down came even close, so thank you so much for your insights :).

  59. Maneo Chou says:

    Answering your curiosity: I searched this up after reading the Swampman thought experiment. To me it seemed ridiculous that the “swampman” is not considered the same person. I have trouble accepting that our existence hinges on the molecules we’re made of because the individual molecules are completely fungible and have no special value to us. As long as my memories and personality are identical I’m the same person no matter what atoms are in me. Even if the swampman were a less than perfect clone, if the personality and memories are similar enough, I think its still the same person, considering the fact that our memories and personalities do in fact change.

    And the fact that so many of the molecules change over the course of our life means that we’re all swampmen. One could try to get all deep and say we’re not the same person we were when we were born, but the point is that the scenario where you die and get replaced with an atomically identical copy wouldn’t be any more special than what we already do from a philosophical point of view… would be a huge deal from the perspective of physics/chemistry though LOL

    Interesting to watch how relevant science and philosophy can be to each other despite using methods that are at odds with each other.

  60. How does carbon dating work then if the atoms in an organic life-form are continually renewed? I googled this topic after reading a comment made about this by comic book writer Grant Morrison and wondered if there was any truth to the idea or if it was a myth.

    • stevegrand says:

      Carbon atoms are constantly being replaced until something dies. After that there’s no turnover. So while something is alive, the ratio of C12 to C14 remains the same as in the atmosphere (where C14 is constantly being created by cosmic rays). After it dies, the existing C14 radioactively decays and isn’t replaced, and so the ratio of 12 to 14 changes over time. By measuring that ratio people can say how long it is since the creature died. If the carbon WASN’T being replaced during life, then we’d know how long it was since the creature or its food first grew, but with the exception of some trees the difference between those two dates is negligible compared to the half-life of C14.

      • dmbaguley says:

        Would I be correct in assuming that once a growth ring is laid down it is effectively dead so the annual nature (Or is it biannual? I don’t remember the mechanism well.) of tree growth makes it relatively easy to account for the unusual nature of trees vis a vis carbon dating? To the extent that any of it is “easy” that is. I suppose if that’s the way it works then one doesn’t carbon date trees, one carbon dates growth rings.

      • stevegrand says:

        >To the extent that any of it is “easy” that is.


        Each ring is just new growth – the stuff underneath is still very much alive and active. I’ve no idea how often it’s recycled but there will still be some turnover. I only mentioned trees because some of them live a very long time and their metabolism is slow. The half-life of C14 is about 5,000 years and the oldest dates it can be used to measure are about 50,000 years, so the life-span of some trees can be several percent of that. The rate of carbon exchange will be slow, so they won’t necessarily have the same 12:14 ratio as the atmosphere right up to the moment they die. I imagine that blurs the result very slightly, but it’s not my field, so I’m probably talking out of my hat! 🙂

      • dmbaguley says:

        Cool, thanks for the quick reply. The only part I was sure about was that it had to do with trees getting *old* sometimes. 🙂

        Even if you are risking talking out of your hat, reading your writing I get the impression you have a safer hat that most for that. To stretch a metaphor way to far. God knows what this stretchy metaphorical hat would have to be made of. 🙂

  61. David says:

    I landed on this looking for how fast we turn over Carbon in our body. I was reading in The Omnivore’s Dilemma about how we can tell how much corn someone was eating based on the C14-C12 ratios, and i was wondering how stable that was over time.

  62. I found you after googling “Richard Dawkins Richard Feynman”, and the youtube clip came up where Richard Dawkins referenced you while talking about the moving sand dune.

  63. Steve, I was very surprised by your response to Jake Reed above. If you’re going to state that somewhere close to 98% of the human body is replaced at the molecular and atomic level, then when someone points out that neurons aren’t replaced, you should investigate the facts rather than overreacting like you did above. Science is continuously evolving and if the facts don’t support your belief, you should reassess how your belief fits into the new paradigm. And maybe it won’t fit, in which case you’d need to reconsider.

    From Mo Castandi’s article on neurogenesis in the human brain: “One side-effect of having a large and complex brain is that you wouldn’t want naïve newcomers barging in,” says Lumsden. “How would new neurons usefully integrate into complex neural networks? If anything, evolution would have made damn sure that mechanisms exist to eliminate these party-crashers. Lack of neurogenesis after the connectional plan of the brain is complete would be a selective advantage.”

    Source: http://www.theguardian.com/science/neurophilosophy/2012/feb/23/brain-new-cells-adult-neurogenesis

    • stevegrand says:

      Hi Julie,

      it wasn’t the facts that irritated me; it was the smug arrogance with which they were delivered! First he tries pulling rank on me (“very prestigious university” and all that) without even bothering to find out who he’s talking to. Then he starts talking down to me, followed by all the unnecessary sarcasm about getting rich, etc. Usually I’m very polite but I can’t stand superciliousness.

      As for the facts and assertions, none of them contradict my point. The (possible) lack of neurogenesis, whether in the HC or anywhere else, makes no difference. Neurons are replaced molecule by molecule. Neurogenesis is increasingly being found in the brain and there is no reason why new neurons should be “naive newcomers” at all. I’m a computational neuroscientist, so I’m pretty confident about that, but I won’t try explaining it now because it makes no difference anyway. Neurons are cells like any other, and they’re in constant molecular flux. That’s why their DNA is so busy. They don’t have to be replaced wholesale, just one protein at a time. If that wasn’t what happens in cells then we wouldn’t need to eat.

      If this guy had been polite then I’d have been happy to discuss the details of his (not always accurate) facts, and even change my mind if the arguments turn out to be persuasive, but I’m not going to waste my time if he just barges in with a supercilious smirk on his face, trying to pull rank, especially as I’m more qualified than he is. I have better things to do with my life!

      The central point that this post was trying to explain is that living organisms are systems in flux – they are not the stuff of which they are made but the organization of that stuff. This doesn’t cease to be true, even if someone manages to find a subset of molecules that hang around for a few decades. Frankly I think this is pretty incontrovertible and obvious (hence me asking why people came here) but it fascinates me how adamant and angry the concept seems to make some people! It makes me wonder what they think is at stake.

      • Dick Lawrence says:

        Both bones and neurons are components of the body that we commonly think of as fixed, but in reality are in a constant flux of destruction and replacement at the molecular level, as this discussion has demonstrated (with some disagreements on the rate of turnover). I’m more interested in neurons, for their role in memory and consciousness, but a recent RPI (Rensselaer) alumnae article discusses research on bones, including the following description:

        “Bones are constantly being remodeled within the human body. Cells produce acids and proteases to break down minerals and proteins in the bone, which are then resorbed into the body. At the same time, to compensate for the resorbed tissue, bones are fortified through chemical deposition and mineralization. This ongoing remodeling process slows down as cells are unable to fully remove bone containing sugary impurities called advanced glycation end-products, or AGEs, which form naturally in proteins.

        “Bone remodeling slows with age, meaning AGEs accumulate at a great rate as we grow older. Individuals with diabetes, certain types of osteoporosis, or metabolic bone diseases are also known to have above-average AGE content. Higher concentrations of AGEs make these groups more susceptible to bone fracture and longer healing time for bone injuries. The chemical PTB has previously been shown to be effective for dissolving AGEs and reducing stiffness in blood vessels for cardiovascular applications. Vashishth said his new study is the first to investigate the effect of PTB on bones.”

        I hope to investigate more on neurons and molecular turnover rates in the future. How memory is encoded in neuronal connections which retain their essential structure over a lifetime, with all the remodeling and replacement going on, is a huge subject, and a great mystery to me at this time.
        – Dick Lawrence

      • stevegrand says:

        Thanks, Dick.

        > How memory is encoded in neuronal connections which retain their essential structure over a lifetime, with all the remodeling and replacement going on, is a huge subject, and a great mystery to me at this time.

        Indeed! Rehearsal must surely be part of it? That’s not an actual answer, of course, just an avenue to explore. It reminds me of one of the earliest forms of computer memory, in which bits were recorded as blips of light on a CRT screen and then read off again by a photocell before the light had time to fade, and sent back around to produce new blips. Now that I think of it, dynamic RAM in a modern computer uses much the same method of constantly refreshing itself, but it’s not such a charming metaphor. If the brain can periodically reactivate small fragments of a memory (e.g. during sleep) then it’s not so hard to imagine how the neurons can maintain their existing patterns of connectivity by “re-experiencing” the stimulus. In such a dynamic system it would also be possible for new neurons to take up earlier patterns and for originally highly specific memories to become more consolidated or otherwise change in their representation in the light of other memories that didn’t exist when they were first laid down. This certainly happens in the artificial brains I’m developing, although I don’t have anything more than suggestive evidence that it happens in natural brains. I think these problems are hard partly because of the vast number of synapses involved – if memory is holographically stored (in a convolved state, I mean, not a literal hologram) then it will be very robust and capable of “moving around” over time, just as long as neurons are capable of re-presenting the stored memory as a stimulus. Mental imagery seems to work by such a top-down re-invocation of sensory experience, so the wiring is there.

  64. Dick Lawrence says:

    a few minutes after seeing your reply, the NY Times published this:


    One of the subsequent comments was: “I often have long-dormant memories and people from my past surface in dreams. I never consciously put my mind on these recollections, but I’ve felt that their appearance while dreaming was my memory refreshing itself.”

    The last few years have witnessed a growing awareness of the plasticity of memory itself. It’s clear that visual memory has very little in common with a photograph, and the reliability of “eyewitness testimony” is far from absolute, with occasionally horrific consequences – alleged perpetrators put behind bars for years or even decades until DNA evidence finally establishes the innocence they’ve maintained all along. Memory seems more like the game of “Telephone” (in which the original message is increasingly garbled or distorted as it passes from person to person); each act of “remembering” a person or event appears to be an opportunity to slightly alter the memory, and you’re less and less remembering the event itself, but rather remembering the last time you remembered it, and then “re-writing” it back into memory, possibly with changes that you’re unaware of.

    I worked professionally designing memory systems for minicomputers. At the time we were still designing the last core memories; semiconductor (dynamic RAM) was just getting started, and I designed experimental systems using CCDs (charge-coupled devices) and bubble memories, which stored bits as persistent stable magnetic domains, moved around by magnetic fields. We played with them all because it wasn’t clear which would become the dominant technology in the future. Interesting work, but unhelpful for yielding insights into how our “meat” memory works.

    Dick L

  65. Cyd Ropp says:

    It seems to me that the answer must be epigenetic information “learned” and stored alongside the structural information that helps the next generation program its replacement parts accurately. I’ve outlined this process in detail at my own blog. http://www.asimpleexplanation.blogspot.com/

  66. David Kellingham says:

    In response in english to: If you came across this post by Googling to find out how many of our bodies’ atoms are replaced each year, would you drop me a comment and tell me WHY?

    I’ve always thought WE are the software and not the human hardware, so I was curious to confirm what Jose Ingenieros wrote about us (our atoms/hardware) being completely replaced every 8 years or so.

  67. Rick says:

    I found this by a Google search. My particular reason was that I was thinking to myself about past mistakes I and others have made.

    Like with your childhood memory example and “you” not being there, it’s sort of a peace of mind to think that “you” weren’t there at the time of those mistakes. While you might still have memories of them, knowing that the atoms that were there, that composed the body you used to make those mistakes, are gone is sort of psychologically relieving.

    Like the body you and others have now aren’t the same ones this or that bad decision years ago. It might sound a bit New Agey, but it does feel something like a rebirth or second chance.

    Imagine, say, finding out your spouse cheated on you years ago. (Not speaking from experience.) They tell you seeking for forgiveness, and so if you wish to forgive, you can sort of think of the body they have now as not being the same one that was cheating on you at that time.

    • stevegrand says:

      You’re not the only one who’s said something like this, and I really wasn’t expecting it. It’s very interesting. I’m really glad you get peace of mind from it. Myself, I still wish life had an UNDO button!

      • Rick says:

        I certainly do too. 🙂
        It doesn’t always help, but when it does it’s a relief.

        I was wondering though, how does it account for things such as the carbon 14 that apparently gets incorporated into our teeth and seems to remain there for life, unlike the carbon 14 in other tissues? I’ve read that they can even date close to the year of someone’s birth just from that, whereas other radiocarbon dating only accounts for time of death.

      • stevegrand says:

        I’m not sure about that, although it seems plausible that they could use the slower rate of turnover in teeth compared to other tissues. Normally we’re constantly replacing the carbon in our bodies, so it keeps almost exactly the same balance of C12 to radioactive C14 that we find in the outside world, where C14 is constantly being produced by cosmic rays. Any C14 that decays is rapidly replaced by fresh stuff from our food. But when we die, we stop turning over carbon, and so the C14 has a chance to decay without any newly made C14 being introduced. Thus the ratio of C12 : C14 goes down after we die but not before, and by looking at this ratio people can work out when we stopped replacing our body tissues. I’ve never heard of anyone being able to date someone or something’s BIRTH from C14 though. The half-life of C14 is 5,730 years, so the time between a human’s birth and death is tiny by comparison to the margin for error. In principle I guess it’s doable – if different tissues turn over carbon at different rates, the C12:14 ratio in teeth would be different from that in muscle, just because it stays around for longer. But that’s some amazing precision, to measure such a tiny difference. Maybe it’s within the capabilities of modern mass-spectrometry? Either way, it would just be a difference in RATE of replacement, not a sign that significant carbon is never replaced. But as I keep trying to get across, it doesn’t make any difference – we’re still not the stuff of which we’re made, even if a tiny bit of that stuff remains in our bodies all our lives. It’s not like that little bit is “magic” and contains the vital essence of life! 🙂

      • Rick says:

        It’s something I’ve come across after taking an interest in this topic. 😉
        Something to do with being able to determine an individual’s year of birth, based on the amount of C14 incorporated into the enamel during its formation. The nuclear tests of the 50s and 60s left a mark in the atmosphere that’s been declining since. By comparing the amount in teeth to the amounts measured in those years and the years since, they can get close to determining someone’s age. On the other hand, I know at least some of the enamel changes all the time, just from remineralizing. Otherwise, all of us would have lost our teeth by now.

        Similar dating supposedly can be done with the lens in the eye.

        In the end, it’s true what you say. As you said, even an atom isn’t the same at every moment. I’m quite content with that. 🙂

      • stevegrand says:

        Ah yes, I hadn’t thought about nuclear testing – that would definitely create a profile in slow-changing tissue. And it reminds me – I need to go to the dentist!

  68. Sawyer says:

    Hey Steve, you asked why so there you have it:

    I googled you after watching this Youtube Video: https://youtu.be/6j3y-3nR-Mg

    I´m a life and dating coach from Germany and often counsel people with heavy childhood issues or bad relationship experiences. Most people believe they are determined by their past.

    I think that something like “childhood” or “ten years ago” or “I just AM a shy person, always have been!” just doesn´t really make any sense and is just a human concept that we believe in. In reality there is no “childhood” and no unchanging or constant identity. These are all just human concepts / illusions. You are the story you tell yourself right now. In the next moment you can be another person if you tell yourself a different story. And in one or two or even 5 years you can be a TOTALLY different person. If you choose to believe that. If not you´re doomed to relive the past again and again and never change for the better or find inner peace and happiness.

    It´s just our believes that keep us trapped in bad versions of ourselves. We just keep the past alive through our memories and fall for this trap. We drag the past into the present moment and into the future instead of saying “Fuck it, I´m gonna be a new person from now on! No matter what happened in my so called past/childhood!”.

    Hope that answers your why-question.

    I believe only two things exist: Energy and empty space. Everything else is opinion. Self, past, solid matter, childhood, positive and negative, problems, mistakes, love, death… these are all just human concepts.

    Most of these matrix concepts (I call this social programming “the matrix” as in the movie) are the biggest roadblocks to personal freedom and true happiness.

    Nice to “meet” you


    • stevegrand says:

      > I believe only two things exist: Energy and empty space. Everything else is opinion.

      Ha! From the perspective of what you do, that makes complete sense. From the perspective of metaphysics I agree with the first part but have a different formulation for the second. Except that the first part then resolves into the second. Only two things exist: energy and empty space. Everything else is FORM. Except that empty space is also form, and form is what we mean when we talk about reality, and so only two things exist: energy and form. Space is what happens when energy takes on form, and so is matter. But metaphysics and personal happiness are different things, so we can come to different conclusions and yet, at a deeper level, mean pretty much the same thing!

  69. Jani says:

    If our memories (those that have survived they decay of time) are actually copies of the original memories and if this pattern of replication is repeated in other particles responsible of our brain functions that eventually form up our consciousness, would it not then be reasonable to say that most of us have already died at least once during our lifetime without ever noticing it?

    • stevegrand says:

      It depends on how you look at it, and who you think “you” are. Are you even the same person that you were yesterday? You have their memories, so it seems as if that was you who did those things, but was it? When you think hard enough about that question, you’re left with the conclusion that all we really “are” is our memories. I can reassemble events from my childhood, but they didn’t happen to this creaky old bag of flesh – they happened to a little boy with freckles and a lot more hair. I have a different body now, made from different stuff, but I inherited his memories because they keep getting maintained as everything else changes. That sounds spooky but it’s not – look at any beach and you’ll find that the pebbles close to the water are smaller than the ones further up. They’re different pebbles from one year to the next, but the ARRANGEMENT of them remains the same – big ones at the top of the beach, small ones nearer the waves. Memories are much the same. So in one way we die many times, in another we’re constantly changing, like the pebbles on a particular bit of beach, and in yet another we remain the same person for a lifetime, until the maintenance process starts to break down, a storm washes away the sand, and we lose our structure.

      • Dick Lawrence says:

        The consensus on the nature of memory has been changing steadily. We once thought that our visual / auditory memories of events were like recordings that we could play back at will and rely on the accuracy of that recording. Research now acknowledges the malleability of memory – it’s powerfully shaped by the state of mind, emotional states, and expectations. This has had the side effect of (realistically) reducing our confidence in “eyewitness” accounts, including from the victim him- or herself. Accounts of assault including rape where we used to take for granted the reliability of witness memory are regularly overturned by DNA testing, in some cases after the accused have spent years of even decades incarcerated.

        It seems there’s an aspect of memory that’s akin to “destructive readout” which is a characteristic of silicon-based dynamic RAM (DRAM) in which stored charge – indicating if it’s a 1 or a 0 in that cell – is destroyed in the readout process and must be restored (re-written) after it’s read. Not saying there is a common foundation to biological vs. silicon memory – just pointing out that every time we recall something, the memory is – or can be – subtly altered. After being recalled and re-stored many times, a memory may bear little resemblance to the original (“objective”) event – without intentionally uttering a falsehood. (Just ask Brian Williams!) When you repeatedly recall an event, what gets re-written is not the original exact replica of memory, but the memory of the previous recall event – hence subject to inaccuracy and distortion.

        I found a similar false memory in my own past: always thought I had seem Jimi Hendrix at Woodstock (’69). Then I studied the timeline and playlist of performers that weekend and discovered I couldn’t have seen Hendrix – I had left very early Monday morning, hours before he went on stage and performed. I did see him a year later at Randall’s Island in NYC 11 months later.

        So back to the Steve Grand blog on memory and identity; I wonder if the malleability (corruptibility) of human memory is due to the repeated process of recalling and then re-storing memory, each time permitting additional changes to the ‘original’ memory, or if there might be some connection to the fact that the atoms, molecules, and synaptic connections that somehow encode long-term memory are being constantly replaced – and potentially at less than 100% accuracy at replicating the original structure and organization. Any comments reflecting peer-reviewed research on memory are entirely welcome !

        – Dick Lawrence

      • stevegrand says:

        I can’t cite you any sources, I’m afraid, but personally I’d go with both of your hypotheses! In my own work, physical refreshing due to the replacement of atoms and synapses isn’t a problem (because I deal with virtual neurons and I can make them as permanent as I want!), so I can’t say much about that possibility. But the further I get into this stuff, the more “holographic” the kinds of memory representation I develop become, and that “suffers” from two kinds of degradation: Firstly, as new memories form, they distort the ones that went before, because they’re all to some extent superimposed. In principle that’s self-correcting, because if one memory distorts another so that it leads to the wrong behavior, the creature will learn from the errors and lay down new memories that adjust things back the other way – the total “hologram” comes to represent a model of the behavior of some aspect of the outside world, and since the world is fairly consistent the model remains self-correcting. But new experiences do distort old ones, and I imagine that sort of thing happens to us too – possibly like your conflation of two concerts. Also, this constant reinforcement of “memory causing behavior causing experiences causing further memories” does seem to drift around a bit sometimes, like Chinese whispers, if the world isn’t being a stern enough judge of the behavior. So although I don’t need to explicitly recall and refresh my artificial memories in order to keep them, the simple fact that memories cause behavior that causes memories does mean they’re constantly recycled. The story sometimes morphs in the retelling!

        Of course I’m talking about procedural memory and your example was of episodic memory, which I have less instinct for. We have pressure to keep episodic memories intact, but at the same time we need to turn them into semantic memories. Remembering last week’s trip to the dentist needs to be kept separate from last year’s, but at the same time I need to develop a *concept* of going to the dentist in general. That seems to me an argument for having quite labile memories that would be prone to corruption as a part of this consolidation. Also, the fact that we call it “re-membering” hints that we actually construct memories from smaller building blocks on demand, and that’s got to be a pretty dynamic and hence mutable process. If a building block gets changed, the memories founded on it will change too. Perhaps episodic memory suffers more from molecular replacement and semantic memory suffers more from a deliberate or inevitable recall-and-re-store process?

        If we develop a small blind spot due to damage in the retina, it disappears from our consciousness very quickly and soon ends up like our permanent “blind spot” – we don’t even notice it’s there. I’ve always taken that to be a sign that primary visual cortex is extremely dynamic, and its structure is “held in place” by constantly seeing things. Take away a bit of that sensory input and the system rewires very quickly (with the consequence that this bit of space simply ceases to exist, instead of being perceived as a hole). If the rest of memory (and surely that’s what the brain fundamentally consists of) is anything like that dynamic, we’d expect it to have to be constantly held in place by new experiences and it’s a wonder we can keep old memories intact at all!

        So I don’t know anything definitive, but if my intuitions are of any value to you then I think you’re probably right on all counts, and like most dynamically stable systems it might be a mixed blessing – we get a robust and powerful system (both physically and informationally) but it comes at the cost of memories that aren’t quite what they used to be!

  70. Shaylin says:

    I stumbled across this website due to looking for answers to human creation and the planet we call Earth. From what I see that you have stated it seems that everything in our body seems to re-generate a new model of it eg. Skin cells die and new ones replace it, so do the bones in our body and Atoms to.

    But how is it that we cannot exceed and adapt to that, as you mentioned that Iron should be of a certain limit it cannot be less and not too high. Why can our body not exceed this and adapt to it to an extent which may change our bodies basic process?

    What would happen if how body did what is was not meant to do eg. fuse atoms or fuse more protons within the nucleus or move our Electrons around to other Nucleus?

    In life we do what we know or have learn and cannot do what we have not learnt, would you say that if our body was aware of its inner abilities like controlling our protons, neutrons, electrons or other molecules within us.

    • stevegrand says:

      Well, as far as protons and neutrons are concerned, we have no control over them because it takes enormous amounts of energy to do that – the sort of energy you find inside the Sun. Electrons are very different – we can move those around from atom to atom using smaller amounts of energy, and that’s called chemistry. But I think I know what you’re saying, and perhaps the answer to your question is evolution? Evolution is capable of learning new things and creating new bodies with very different processes going on inside them. For instance, long ago there was a species of land animal that looked something like a hippopotamus. It was probably happy enough semi-submerged in mud and water, but if you were to throw one of them into the ocean it would drown. But over millions of years some of these creatures gradually got better at living without air and evolved into whales. They still need to breathe, but their chemistry changed to make it possible for them to dive deep and stay under water for a very long time without dying. And of course long before that happened it all happened the other way round! All land animals that exist today evolved from water animals. Life started in the water. Mammals like us eventually evolved from a kind of fish (other types, like modern insects, say, evolved from different kinds of sea creature). Our distant ancestors had to gradually change from breathing water through gills to having lungs and breathing air, and a lot of their other systems had to change to make that possible. But it happened.

      Yes, like you say, in life we cannot do what we haven’t learned. But through trial and error we can eventually learn how to do something new (ride a bike, say), and from then on we can always do it, and we can teach our children how to do it. Evolution is just trial and error applied to the shapes of our bodies and the chemical reactions that go on inside of them. The “teaching” is done by passing our genes down to our children. It’s VERY capable of learning new tricks. We don’t need to CONTROL or be aware of our inner abilities for this to happen. We just have to be born very similar to, yet slightly different from, our parents. That’s really all it takes!

      If you don’t believe that (and I know many people don’t believe in evolution, usually because they’ve been lied to or misled by people who don’t have a clue what they’re talking about and have ulterior motives) then I’d be happy to explain – just let me know. I know it works, because I do this stuff for a living. We’ve changed our bodies’ basic processes many times over our history. We can’t change iron into something else, because that would take vast amounts of energy, but we can change the amount of iron we keep in our bodies and what it’s used for – it just takes a long time for that to happen. But there HAS been a very long time since life began.

  71. Phil says:

    Carbon 7

    • Phil says:

      Though incredibly complex, the basic concept as a whole is expressed fairly simply: 666 = human, 616 = the more fluid and insubstantial being we will precipitate out of the “formless,” or metarealm, for continued interaction with 3D planes. In other words, to create anything at all you have to have two things and bring them into union. The local, seriously stepped down and ultimately false correspondence on our level is the physical union between a man and a woman to make a child. I say false because, as always, the appearance of it isn’t really what is happening. The result of that (bigtime orgasmic) synthesis creates a third (or more) thing. Your consciousness is not nothing. Thought is stuff, things. When your consciousness merges with your metaself, it is stuff merging with other stuff through the union just discussed, a new entity will become and which will then have the facility to precipitate a carbon 7 “body” as needed in this, or other, plane/s. This instantly precipitated body will have all of the attributes of superhuman capabilities so often talked about in so many sources. After all, it’s going to take the much less substantial carbon 7 version of us to be able to walk through walls.

  72. I came here from a search trying to compare how often atoms are replaced to how often cells are replaced, but I was actually interested in the specific rate to set up someone for a joke on their birthday. I ended up looking up the atom replacement rate because the cell replacement rate was much lower than I thought.

  73. interested says:

    I just wanted to get my head round the lifecycle of atoms. Scientifically I am aware that atoms are not created but then how do our bodies grow in the womb from nothing and plants grow from seeds etc etc – are they not creating atoms ? I know the answer is they are not but I wanted to get some proper scientific explanation for it on the web – and so far I have come no articles explaining this

  74. Cathryn Hatle says:

    People are still looking up this question out here–it might be the “suchness of the moment”, an idea whose time has come, something in the air.

    My entry to this question was metaphysical. I am a very lay reader and tend to follow questions that pop up in front of me. As an elementary teacher (1-3 grades) I have had MANY intriguing metaphysical questions posed to me, as a retiree I now have time to think about some of these.

    Lay research has led me through Buddhism, popular theoretical physics explanations (which I TOTALLY get, as long as my eyes are still on the words), economics (economists sound like such intelligent people, why do they hold such stupid ideas?) evolutionary theory, the origins of consciousness, consciousness in other species, science fiction. Also, as I have aged, the dualism that I was taught makes less and less sense; I do not experience the mind/body split the way I did when I was much younger (Do you love me for my body or my mind?)

    So an idle speculation–Are we transient twists in the energy field?–led to wondering about the preposterous existence of consciousness and the persistence of memory and the further idle wondering about how much our “body” interacts on a atomic level with the universe? I don’t have the background or jargon/vocabulary to pose that question more clearly.

    Looking at previous comments, there is a range of interest and backgrounds, want to make sure that idle speculators are represented also.

  75. Jordan says:

    “If you came across this post by Googling to find out how many of our bodies’ atoms are replaced each year, would you drop me a comment and tell me WHY?”

    I am interested in whether we sort of “die” every so often and if so, how often. If every atom that makes up my body at this instance, in particular my brain, is replaced eventually, that would make the “me” that exists right now gone, no?

    • stevegrand says:

      🙂 I reckon the answer depends on what you mean by your quote marks! In some ways even the “you” who existed just yesterday is gone now. That “you” ceased to exist overnight – it’s not like you spent the night awake inside your head, staring at a blank screen; you were no more existent as a conscious being than you were a billion years ago. Yet this morning someone became conscious and inherited the memories of someone who lived yesterday, and naturally you believe that you were the one who experienced those things…

      I suspect there are few studies on this because on the one hand it’s self-evidently obvious – we all know our cells die, so what is there to prove? But on the other hand it completely messes with our sense of identity, and sometimes we just don’t go down roads we feel uncomfortable about. And then to make it worse, it’s a question about probability, and the human brain doesn’t deal well with probability. There’s no real answer to “how often,” because we’re dealing with half-lives. We can say that on average half of our molecules are replaced over a given period, but some of them are replaced much sooner and some may never get replaced at all, purely by luck. Really it doesn’t matter much what the various half-life values are – the important thing is that we’re constantly in flux and therefore what we “are” is not the stuff from which we’re currently made. We are the self-maintaining arrangement of that stuff. But so is everything else, if you know how to look at it right, so really we shouldn’t be surprised by this! 🙂

  76. Jordan says:

    I’m also surprised that it seems there is relatively few studies relating to this (perhaps I am wrong.) The main one that keeps popping up is the one from the 50’s, and then I saw this one from another commenter- https://stevegrand.wordpress.com/2009/01/12/where-do-those-damn-atoms-go/#comment-6077

  77. Elizabeth Rounds says:

    Very interesting posts! At 64 years I am putting the Harley aside to read up on quantum theory, parallel universes (and more) and googled “Where do the atoms go” . Voila – here I am and just want to thank you, Steve, for this has given me even more incentive to research and learn! Never too old! Liz R.

  78. I was interested to find out how come our brains and eye lens clearly age through our life, yet like many others I had read through Bryson’s book that we are replaced. I got to this site which showed how often different cells are replaced in different parts of the body: http://book.bionumbers.org/how-quickly-do-different-cells-in-the-body-replace-themselves/ – It seems the eye lens being a crystalline structure maybe does not get replaced even at the atomic level? But then I wanted to know more about the atomic replacement and that took me to your page. Having read your article now, which was very informative, I am going to check out your comments on dualism… Ordinarily I think the term dualism refers to the powers of good vs evil, but I think you have used the same term to discuss matter and spirit? As a believer in theistic evolution (see http://www.biologos.org if you want to know more – it is not ID – Francis Collins was the founder), I don’t see a conflict between us being continuously physically recreated and us having a spiritual aspect which is eternal (and I suppose in the realms of faith rather than science), it just makes creation all the more remarkable and wonderful.

    • stevegrand says:

      > but I think you have used the same term to discuss matter and spirit?

      Yes, I meant Cartesian Dualism, rather than Moral Dualism.

      Interesting to hear your perspective – thanks for that! I have some sympathy with Collins’ ideas and hopes, but it is only heartfelt sympathy, not agreement. Something I’ve long found interesting but never been able to explain in a way that anyone seems to ‘get’ is that if it weren’t for the rational but somewhat arbitrary way in which our species developed its understanding of the world over the last few thousand years, the entire notion of gods, whether as persons or prime movers, would never have come into existence. We wouldn’t even have thought of it. But because it DID come into existence, it can’t be un-invented, and hence carries far more weight and unquestioned credence than it deserves and we realize we’re giving it. Meanwhile, the theories of transcendent philangily and sophic asturnance don’t even figure in anyone’s search for truth and meaning at all. Mostly on account of the fact that I just made them up! If it weren’t for a series of historical accidents of logic, gods and eternal spirit would carry no more significance than sophic asturnance. It’s almost impossible to put that genie back in the bottle now, though, and it ends up seeming like a ‘good’ explanation for things when it only seems that way because we’ve got used to it being an explanation at all. Starting from a blank sheet it might never even make it to the level of hypothesis. It’s hard to explain what I mean, because of the very nature of it already being ‘out there’ as a competing explanation with thousands of years of momentum. But I think starting from a blank sheet there are much more defensible, yet at least equally profound and heartening, ways to think about the problems that historically gave rise to gods. If I ever get any spare time I want to write a book about another way to think about spirit. I don’t actually know what the answer is, but in the past I’ve found that writing books about something is a good way to discover what it was you had to say! Hopefully if I do that you’ll come across it and read it, and then we’ll have two theories to compare and contrast! 🙂

  79. Delanie says:

    I am replying to your edit question. The reason I looked up why we lose 98% of our atoms in a year is because of my intro level biology class. It is online and opposed to reading the book I decided to good answers and read it for myself. Thanks for the help!

  80. The Dandy Highwayman says:

    I ended up here after re-reading a brief conversation we had on my own blog just over eight years ago. Cor, what a pompous twat I was. Still, it was a good exchange. I found myself wanting to read the book you were working on so Googled for it… but “Steve Grand spirit” only gave me results about America’s first openly gay country singer. Did you ever write “Spirit”?

    • stevegrand says:

      Whoops, nearly missed this, sorry. I remember you, but I can’t for the life of me remember what we discussed. Either way, I’m sure being a pompous twat is all part of the process and afflicts us all! Nope, not written Spirit yet – working on a new artificial life game and it’s running a little bit (7 years) over schedule! For the book I’m still waiting to recharge my stock of metaphors and anecdotes, but life is too much like firefighting at the moment. It will get written, though. Possibly on my deathbed… And yes, the other Steve is quite an alter ego for me to live up to! 🙂

      • The Dandy Highwayman says:

        Ah, I look forward to reading it when it does get written (hopefully before you are on your deathbed!). Having spent many happy hours editing the genomes of Creatures, I look forward to your new game too.

  81. panchkarma27 says:

    Thanks for sharing the useful information. It is really a great blog.

  82. May Prince says:

    Not trying to be crude here, and yet I kind of get the impression that you already managed to cite “the direct source” when you have cited the New York Times article from October 1999 that explained the chronology of the whole neurogenesis debate since I believe most of the biology folks making an entrance here may agree that a neocortex is of the greatest importance. It is only that the citation does not directly contain the words “atoms recycled every year” and yet I feel that it still acted well as the citation that sums up the whole point.

  83. Adam says:

    I’d like to propose a thought experiment that a friend of mine and I have disagreed about, and I’d really appreciate it if you could perhaps write on this topic or at least comment on your opinions. Do you believe that the human conscious, or this idea of “self” is a product purely resultant from matter? The alternative is some metaphysical manifestation that is unique to us that gives us our sentience/sapience. If you agree with the former then I’d like your answer to our discussion, and if you believe the latter, consider the former to be true hypothetically. A machine exists in the future such that we have the ability to measure every quality of every atom in the human body, every subatomic particle, and every wave, with the ability to transmit that information to another machine that assembles you from new atoms perfectly recreating your body and brain. The first machine then destroys your first body. What is your interpretation of what would occur in regards to the “self”, or conscious in that scenario? Would you use such a machine?

    If I may just give my personal belief. I expect, as I walk into this machine, my current body, my experience, unique to me, my stream of consciously made up of all my senses would end instantly. On the other end a copy of me with all of my memories, made of matter that did not experience anything that I did personally but has those memories that my matter did and would go on functioning in a society exactly as my first body would have.

    My friend’s interpretation is that it would be akin to going through a surgery, where you have a break in your stream of consciousness and simply wake up in a different place and continue living your life in a different body.

    Thanks in advance,

    • stevegrand says:

      Sorry for the delay, Adam – I haven’t updated this site in years. I wrote about exactly such a machine in my first book (Creation). The bit about ‘destroying the original’ is how people avoid dealing with the fact that there would now be two of you! Why destroy it?
      Memories are what you consist of. Memories and predictions. Future and past. We have no access to the present, which has already gone. Mind-bending thing to think about, isn’t it?

  84. Chris says:

    Oh my gosh, *finally* someone who thinks about life and matter in the manner I have concluded is likely the accurate understanding, too. There are loose ends – questions still to be asked – however, but not here. If you’re open to dialogue, you have my email.

  85. Pingback: As 10 principais coisas que abalarão sua percepção da realidade - Replicario

  86. Pingback: Top 10 Things That Will Shatter Your Perception Of Reality - article

  87. Addy Pross says:

    Steve, your comment in Creation: “the most important law of nature: things that persist, persist, and things that dont, dont” was genius. It has been a central theme in my origin of life thinking for several years now. I believe that without realizing it that you extended the Second Law of Thermodynamics in a way that enables the existence of living things to be accommodated in physical thinking. At first I thought your stating the obvious was no big deal. After all, tautologies are tautological, no? But it was. Like Thomas Huxley’s comment on evolution: “How extremely stupid not to have thought of that!” I feel the same way. Anyway in my talks and papers I now give you the full credit for having intuited “the most important law of nature”. Bravo!

    • stevegrand says:

      Thanks Addy, you brightened my day! Sometimes I say dumb things like that and people just think I’m being dumb – it’s nice when they’re appreciated. I just watched an interview with you on YouTube and very much enjoyed it. I shall read your book! More power to your elbow!

      • addy pross says:

        Thanks Steve. Yes, clearly dumb is also in the eye of the beholder. Anyway immensely satisfying that a simple commonsense notion – persistence – is able to connect physical, chemical and biological understanding – but only if you are persistent!

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: