Between a rock and a hard place

Today I went out, ostensibly to think about my game. I went to Slide Rock in Sedona, where a canyon creek produces a delightful water slide, and bottle-green water cascades through brilliant red rocks as if designed for a film set. Unfortunately I was in a bit of a delicate mood and there were also a lot of women in bikinis, so not much thinking got done and therefore I have nothing to blog about.

I sat opposite a spot where people could jump about 15 feet into the water below, which they did with gay abandon until a pretty, preppy girl of about 18 called Jessica came along. She walked up to the edge, hesitated for a moment and was lost. She chickened out and withdrew in a flurry of nervous giggles. But she had a couple of friends on my bank, who hollered at her for being such a wimp and generally tried to encourage her, thus making it ever harder for her to get up the nerve. She tried again, and chickened out big time. People started to notice, but she bravely kept on trying, and kept on chickening out again. After about ten minutes it had become a major life ordeal for her, and had drawn a crowd of about a hundred of us who were helpfully counting to three and chanting “Jump! Jump!” at the poor girl. Can you imagine? By now it was completely impossible for her and she walked away, with shame and bitter disappointment seething inside her. I really felt for her.

Anyway, up above all this, taking no notice whatsoever, was a small hoodoo, on which sat a precariously balanced cap rock, whose only mistake had been to have a crack in one side, a thousand years ago, which had widened and isolated the rock from its neighboring strata. Once water had seeped into the crack and found its way to the soft sandstone below all was lost for it, too, and it gradually became marooned on a pinnacle of sand, maybe three inches across, from where, unlike Jessica, it will soon plunge into the foaming depths below.

Those foaming depths are formed into a series of potholes, because once such a rock falls into a hollow it can’t float out again, and hence acts as a millstone, grinding and digging itself an ever deeper and more inescapable hole.

The potholes in turn alternated with beaches, because of the way that, once a river starts to churn and bend, the outside of the bend gets the brunt of the water and debris, and so gets carved deeply, while the inside ends up with a slower current and consequent deposition. Once the process has started it can’t stop, until eventually the curve becomes horseshoe-shaped and a flood breaks through the ever thinning wall to produce an oxbow.

And the pebbles on these beaches were graded very neatly, with all the big stones at the top and all the finer ones at the bottom, not because God had carefully arranged them for best effect but because small stones can fall through the gaps between big stones, but big stones can never fall through the gaps between small ones.

And the people who sat on these beaches laughing at Jessica were arranged in clumps that drifted, rose and fell rhythmically during the afternoon, because everyone finds themselves in a tension between the desire to be with other people and the desire not to be seen to stand too close to strangers. As the gaps between them fill they find themselves in a crowd and wander off to find some space, thus becoming a nucleus for further aggregation.

And the level of noise rose and fell too, as each person had to speak louder to be heard over the others, who in turn had to speak even louder, until the crescendo reached the point where someone paused in their conversation to wonder why everyone else was shouting, then others wondered why that person had suddenly stopped talking and stopped too, and then finally those who were a bit slow on the uptake realised that they were the only ones left speaking too loud.

I have absolutely no reason to tell you any of this other than to remark on how amazing it is when positive feedback meets negative feedback and each has a time delay. The result is self-organisation. The result is also very beautiful, and anyone who thinks all this order needs a designer is sadly mistaken: you only have to look at things which have been designed to see that they can’t compare. Only randomness ratcheted by selection and driven by feedback can produce such elegance. Self-organisation blows my mind even more than women in bikinis.

And meanwhile, whilst everybody was kicking the pebbles and wondering about the noise and remarking at the tops of their voices to their neighbours about whether that hoodoo was safe to walk under, Jessica realised that no-one was looking any more, stepped up to the edge and jumped, bless her. I think it probably made her week.

Luckily the rest of us noticed in time to cheer.


I refute it thus… Ouch!

Following on from the John Searle interview, Paul Almond and I have been having quite a lengthy discussion about what reality means. Usually I’m the extreme one because of my argument that some things that exist only in computers are just as real as those that exist in the so-called physical world, but this time I seem to be the moderate (or reactionary?) one because Paul believes everything is real and his office chair is Albert Einstein (well, sort of, anyway). If you’re interested, the conversation is over at Machines Like Us.

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!