Wolfram Science Group
Phoenix, AZ USA
Registered: Aug 2003
Thanks for your note. I will try to clarify what I was saying. I had said -
"The point is, once you have a seperate 'motor' making underlying complexity for reasons entirely distinct from natural selection, there is no reason to expect selection to operate toward complexity rather than away from it."
Notice, I did not say it can't ever operate toward greater complexity. It might, it this or that case. But the reason to suppose natural selection must be capable of generating all the complexity we see, disappears when that complexity is adequately explained by another mechanism.
You said -
my e-mail on which he was commenting said, "On January 31, 2003, I sent you an e-mail with my idea of why redundant mechanisms for the same effect may be favored in biology." The gist of the earlier e-mail was that the need for hybrid vigor in biology may be the driver of increasing complexity in biological evolution.
Yes, I understood the point. Something redundant in A may be useful in A crossed with B, and therefore help A have more descendents without ever helping A directly. I restate the point so you can see I got it.
But it is one thing to show that redunancy may sometimes convey a selective advantage, and other to establish that (1) it generally does (2) that this outweighs optimizing improvements that may reduce complexity (3) that natural selection, operating on whatever level of selective advantage complexity confers, has actually caused all of the complexity (not just organism to organism differences, but complexity of structure or form within individual types) we see in the natural world.
If, instead, biological systems use simple programs from some limited class to perform a given construction, then one expects the variety those programs exhibit to be exhibited by those biological systems, without any more ado and long before any selection comes in. Selection might then favor redunancy too. Or it might prune out a few of the simple program behaviors as unfit. Or optimize slightly for this or that niche. But the complexity would already be there, natural selection would be operating on it, and would not be the underlying cause.
For example, shell fish aren't adaptively selected for widely varied pigmentation patterns, some of them of extreme intricacy. It isn't that shell fish with plain patterns don't make it - there are scads of those too. Nor that only a variety of patterns allow exploitation of a variety of niches. There is really no evidence it makes any difference to any of them, frankly. Instead, all the patterns made by a class of simple programs of one definite type are used.
The whole class of organisms has some "hack" for their shell patterns, and which switches are in which position are essentially random from species to species. Many of those switch position combinations give simple behavior. Some give complicated behavior. Why? Just because that mix is what simple programs typically do, so they do it here, too.
How can we tell this is what is going on in the case of the shell patterns, rather than some elaborate selection favoring complicated rather than simple patterns? Because essentially the entire parameter space is populated by one species or another. There is no sign certain types have been dropped by natural selection. Nothing is missing. The space of the simple program outcomes (with the right parameters) and the space of the shell patterns match.
If instead we looked and saw that only the complicated patterns remained, and the simple ones were missing, *then* we could say that complexity had been selected for, and that the complexity we see is the result of natural selection in favor of complexity. In some other biological case, maybe that happens -and your sort of explanation of a survival value to redunancy through hybrids working might describe why that is happening, perhaps. But sometimes there is no need for it.
Now, back to my quote from my previous. I say "no reason to suppose" natural selection tends toward complexity rather than away from it. That does not mean there is no possible situation or cause whereby natural selection might favor a complicated outcome in case N. It means I can see possible situations or causes whereby it might favor complexity in case N (say redunancy value in hybrids), and others whereby in might favor simplicity (say some optimized wing shape, always exactly "so") in case M. Which way does it go, net? That is an empirical question. I don't know, a priori.
Before I had the algorithimic means of generating complexity, I had a reason to suppose natural selection favored complexity, net. Not based on one mechanism that might do so (e.g. redundancy confering survival value) - that is from the model side, if you get me. But before, I had a reason to suppose it must, from the data side. I didn't have anything else to ascribe the existing complexity I can see in the data, to.
(Kauffman's random spillover into an "adjacent possible" is about it, otherwise. Or another version of much the same thing, Gould's observation that it started simple so where else could it go, just randomly walking?). It is obviously there. Something is causing it.
Before I saw it could come from the nature of the simple programs that life happens to be using, I had to ascribe it to natural selection as the only plausible cause available. Now, I don't. I can match the data without that assumption. It has gone from something I thought had to be so a priori to something that may or may not be so empirically.
Now, look also at the fossil record and think about the rates at which these things seem to happen. You've got survivals forever like the bacteria. No sign of a strong force weeding out the simpler types there. The simple types are still around. In raw numbers, generations, time on earth, they are the most successful organisms. Without any of the later hacks, with less redunancy than higher sexual animals, etc.
Then we've got the Cambrian explosion - all these widely varied types in a tiny geological window, from practically nothing just before. Then no great incease in types for a long time, and even some pruning of the bushy tree of types. Is that the pattern one expects from natural selection operating in favor of redunancy, everywhere and always?
But suppose, hypothetically, that you just reached a programming level with 10-100 new switches, then you'd expect every possible combination of those switches very soon. n^10 or n^100 new forms, bang (some so close we wouldn't distinguish them, to be sure). Some are unsound and disappear. A giant possibility space is already populated. Natural selection then goes to work on an already bushy tree of types. Maybe it favors redundancy and keeps certain things around, maybe it optimizes for a few niches in this or that case.
Which fits cases like the Cambrian better? Or cases like the shell patterns?
Obviously, both can be going on. But which is really causing the variety we see, and complicated rather than simple individual forms, is an empirical question. We can address it, though loosely, by seeing which fits the data in more plausible ways. You may very well find cases where a survival value to redundancy is clearly the cause of some level of remaining variety - wherever it originally came from. You may even find a case where it is clear that is where it originally came from, too (though that is harder to see or to establish).
But what was there before and isn't there anymore (post NKS I mean) is the notion that natural selection has to be the mechanism and we only have to figure out how it could possibly favor complexity. It doesn't have to be the mechanism. Natural selection doesn't *have to* operate, on average, in favor of complexity. If it *does*, that is an additional and empirical result to try to establish, and requires more than arguing it could because sometimes it has a survival value.
I hope this helps.
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