2012-04-30

Darwin was (half) wrong

Slashdot ran a story, "The science of handedness". I'm pretty sick of reading this sort of thoughtlessness describing evolutionary biases. If you're going to say that an adaptation gives a reproductive or predatory advantage, then fine, you're talking Darwinian evolution -- survival of the fittest -- and that's pretty trivially easy to show, even in a lab. If you're going to say, "Everybody in chummy societies had the same handedness so they could share tools", then please tell me how that weak-sauce tiny (or effectively zero-magnitude) biological fitness bias is supposed to have produced a genotypic change to an entire species within the known anthropological lifetime of the species. Remember that Darwinism requires that for your random trait variation to survive and thrive, at a minimum you have to pass your genes on while somebody else does not. So, I have to wonder if the authors "believe in" Darwinism or if they do not.

This gets at what I think is a much bigger issue: fundamental to Darwinism is not just survival of the fittest, but also randomness. I think that true biological evolution -- what's actually happening in the real world -- is not Darwinism, because it is very non-random. It is inconceivable that the complexities of the human organism, or any other for that matter, could have occurred by chance via a random walk through the state-space of possible genetic mutations (many of which could easily give rise to non-viability) in the number of generations since the major forks in the tree of life. There just isn't enough time, enough generations. There isn't sufficient evidence of non-viability, through miscarriage etc., for the worst mutations to die out -- and there isn't sufficient evidence that most traits that are said to evolve through "survival of the fittest" actually gave the possessor of that attribute an actual survival advantage, a reproductive advantage or an advantage as a predator, at the expense of those that did not possess that attribute.

What's the alternative? Even setting religious issues completely aside, personally I think that built into every feed-forward mechanism in biology, crossing back across vast numbers of levels of emergent complexity, are corresponding feed-BACK mechanisms (actually, back-propagation mechanisms, to use the machine learning terminology) such that a system's biology -- and even its genome -- can "learn" in response to environmental stimuli. Everything we have come to understand about learning and optimization from the field of machine learning supports the hypothesis that to learn anything, at any appreciable rate, you must introduce feedback loops that back-propagate the error between expected and observed in some way such that the model can be updated to reduce the error for future predictions. In other words, mutations (and epigenetics) are very NON-random, driven by the environment and by life-experiences and even by the conscious choices of the host organism. This is much less about Lamarckism (although epigenetics are proving Lamarck was pretty much right) and much more about *directed* evolution (i.e. evolution being a biological learning and optimization problem).

In summary, I claim that Darwin was (half) wrong: evolution is about fitness, but optimizing for a given fitness function is not necessarily a random walk.