Saiba por que tudo que lhe ensinaram sobre evolução está errado

sexta-feira, março 19, 2010

Why everything you've been told about evolution is wrong

What if Darwin's theory of natural selection is inaccurate? What if the way you live now affects the life expectancy of your descendants? Evolutionary thinking is having a revolution . . .

Oliver Burkeman

The Guardian, Friday 19 March 2010

Read the first part here/Leia a primeira parte aqui

...Far more than biologists, evolutionary psychologists bought in to the ultra-simple version of natural selection, and so they stand to lose far more from advances in our understanding of what's really been going on. They were always prone to telling "just-so stories" – spinning plausible tales about why some trait might be adaptive, instead of demonstrating that it was – and numerous recent studies have begun to chip away at what evidence there was. (That waist-to-hip ratio finding, for example, doesn't seem to hold up in the face of international and historical research.) And now, if epigenetics and other developments are coming to suggest that environment can alter heredity, the very terms of the debate – of nature versus nurture – suddenly become shaky. It's not even a matter of settling on a compromise, a "mixture" of nature and nurture. Rather, the concepts of "nature" and "nurture" seem to be growing meaningless. What does "nature" even mean if you can nurture the nature of your descendants?

This is one central argument of Shenk's new book, subheaded Why Everything You've Been Told About Genetics, Talent and IQ is Wrong. All our popular notions about talent and "genetic gifts", he points out, start to collapse if the eating habits of Tiger Woods's ancestors, for example, might have played a role in Woods's golfing abilities. (Woods always crops up in discussions on the origins of genius; more recently, he has started cropping up in evolutionary psychology discussions about whether promiscuity is inevitable.)

"What all this evidence shows is that we need a much more subtle and nuanced understanding of Darwinism and natural selection," Shenk says. "I think that's inevitably going to happen among scientists. The question is how much nuance will carry over into the public sphere . . . it's really funny how difficult it is to have this conversation, even with a lot of people who understand the science. We're stuck with a pretty limited way of viewing all this, and I think part of that comes from the terms" – such as nature and nurture – "that we have."

Among the arsenal of studies at Shenk's disposal is one published last year in the Journal of Neuroscience, involving mice bred to possess genetically inherited memory problems. As small recompense for having been bred to be scatterbrained, they were kept in an environment full of stimulating mouse fun: plenty of toys, exercise and attention. Key aspects of their memory skills were shown to improve, and crucially so did those of their offspring, even though the offspring had never experienced the stimulating environment, even as foetuses.

"If a geneticist had suggested as recently as the 1990s that a 12-year-old kid could improve the intellectual nimbleness of his or her future children by studying harder now," writes Shenk, "that scientist would have been laughed right out of the hall." Not so now.

And then there is Jerry Fodor, the American philosopher. I started reading What Darwin Got Wrong, the new book he has co-authored with the cognitive scientist Massimo Piattelli-Palmarini, one morning, along with that day's first coffee. A few pages later, as the coffee kicked in, I grasped with astonishment what Fodor had done. He hadn't just identified evidence that natural selection was more complicated than previously thought – he'd uncovered a glaring flaw in the whole notion! Natural selection, he explains, simply "cannot be the primary engine of evolution". I got up and refilled my cup. But by the time I returned, his argument had slipped from my grasp. Suddenly, he seemed obviously wrong, tied up in philosophical knots of his own creation. I alternated between these two convictions. Was Fodor's critique so devastatingly correct that his critics – Dawkins, Dennett, the Cambridge philosopher Simon Blackburn, and many others – simply couldn't see it? Had he actually managed to . . . but then it slipped away again, vanishing into mental fog.

I called Fodor and asked him to explain his point in language an infant school pupil could understand. "Can't be done," he shot back. "These issues really are complicated. If we're right that Darwin and Darwinists have missed the point we've been making for 150 years, that's not because it's a simple point and Darwin was stupid. It's a really complicated issue."

Fodor's objection is a distant cousin of one that rears its head every few years: doesn't "survival of the fittest" just mean "survival of those that survive", since the only criterion of fitness is that a creature does, indeed, survive and reproduce? The American rightwing noisemaker Ann Coulter makes the point in her 2006 pro-creationist tirade Godless: The Church of American Liberalism. "Through the process of natural selection, the 'fittest' survive, [but] who are the 'fittest'? The ones who survive!" she sneers. "Why, look – it happens every time! The 'survival of the fittest' would be a joke if it weren't part of the belief system of a fanatical cult infesting the Scientific Community."

This argument, perhaps uniquely among all arguments ever made by Coulter, feels persuasive, not least because it is a reasonable criticism of some pop-Darwinism. In fact, though, it's entirely possible for scientists to measure fitness using criteria other than survival, and thus to avoid circular logic. For example, you might hypothesise that speed is a helpful thing to have if you're an antelope, then hypothesise the kind of leg structure you'd want to have, as an antelope, in order to run fast; then you'd examine antelopes to see if they do indeed have something approximating this kind of leg structure, and you'd examine the fossil record, to see if other kinds of leg died out.

Fodor's point is more complex than this, although it's also possible that it is not really a point at all: several reviews of the book by professional evolutionary theorists and philosophers have concluded that it is, indeed, nonsense. As far as I can make out, it can be summarised in three steps. Step one: Fodor notes – undeniably correctly – that not every trait a creature possesses is necessarily adaptive. Some just come along for the ride: for example, genes that express as tameness in domesticated foxes and dogs also seem to express as floppy ears, for no evident reason. Other traits are, as logicians say, "coextensive": a polar bear, for example, has the trait of "whiteness" and also the trait of "being the same colour as its environment". (Yes, that's a brain-stretching, possibly insanity-inducing statement. Take a deep breath.) Step two: natural selection, according to its theorists, is a force that "selects for" certain traits. (Floppy ears appear to serve no purpose, so while they may have been "selected", as a matter of fact, they weren't "selected for". And polar bears, we'd surely all agree, were "selected for" being the same colour as their environment, not for being white per se: being white is no use as camouflage if snow is, say, orange.)

Step three is Fodor's coup de grace: how, he says, can that possibly be? The whole point of Darwinian evolution is that it has no mind, no intelligence. But to "select for" certain traits – as opposed to just "selecting" them by not having them die out – wouldn't natural selection have to have some kind of mind? It might be obvious to you that being the same colour as your environment is more important than being white, if you're a polar bear, but that's because you just ran a thought-experiment about a hypothetical situation involving orange snow. Evolution can't run thought experiments, because it can't think. "Darwin has a theory that centrally turns on the notion of 'selection-for'," says Fodor. "And yet he can't give an account – nobody could give an account – of how natural selection could distinguish between correlated traits. He waffles."

Those of us baffled by this argument can take solace in the fact that we're not alone. The general response to Fodor among evolutionary thinkers has been a mixture of derision and awkwardness, as if one of their previously esteemed colleagues had entered the senior common room naked. Says Dennett, via email: "Jerry Fodor's book is a stunning demonstration of how abhorrence of an idea (Jerry's visceral dislike of evolutionary thinking) can derange an otherwise clever thinker . . . a responsible academic is supposed to be able to control irrational impulses, [but] Fodor has simply collapsed in the face of his dread and composed some dreadfully bad arguments." What Darwin Got Wrong, Dennett concludes, is "a book that so transparently misconstrues its target that it would be laughable were it not such dangerous mischief".

It would be jawdroppingly surprising, to say the least, were Fodor to be right. A safer, if mealy-mouthed, conclusion to draw is that his work acts as an important warning to those of us who think we understand natural selection. It's probably not a bankrupt concept, as Fodor claims. But nor should laypeople assume that it's self-evidently simple and exhaustively true.

The irony in all this is that Darwin himself never claimed that it was. He went to his deathbed protesting that he'd been misinterpreted: there was no reason, he said, to assume that natural selection was the only imaginable mechanism of evolution. Darwin, writing before the discovery of DNA, knew very well that his work heralded the beginning of a journey to understand the origins and development of life. All we may be discovering now is that we remain closer to the beginning of that journey than we've come to think.

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Fui, sem saber por que, pensando -- onde que o fato, Fato, FATO da evolução foi realmente um fato, Fato, FATO científico devidamente corroborado pelas evidências no contexto de justificação teórica? Que eu saiba, nunca. Desde 1859...