Friday, April 23, 2010

Coyne on Dawkins, Fodor, and Piattelli-Palmarini

Jerry Coyne is an evolutionary biologist at the University of Chicago. He has a long review that covers both Richard Dawkins' The Greatest Show on Earth: The Evidence for Evolution and Jerry Fodor and Massimo Piattelli-Palmarini's What Darwin Got Wrong.

Coyne starts with Dawkins, supporting his position on evolution.
Imagine for a moment that a large proportion of Americans--let's say half--rejected the "germ theory" of infectious disease. Maladies like swine flu, malaria and AIDS aren't caused by micro-organisms, they claim, but by the displeasure of gods, whom they propitiate by praying, consulting shamans and sacrificing goats. Now, you'd surely find this a national disgrace, for those people would be utterly, unequivocally wrong. Although it's called germ theory, the idea that infections are spread by small creatures is also a fact, supported by mountains of evidence. You don't get malaria unless you carry a specific protozoan parasite. We know how it causes the disease, and we see that when you kill it with drugs, the disease goes away. How, we'd ask, could people ignore all this evidence in favor of baseless superstition?

But that's fiction, right? Well, not entirely, for it applies precisely to another "theory" that is also a fact: the theory of evolution. Over the past quarter-century, poll after poll has revealed that nearly half of all Americans flatly reject evolution, many clinging to the ancient superstition that the earth was created only 6,000 years ago, complete with all existing species. But as Richard Dawkins shows in his splendid new book, The Greatest Show on Earth, the theory of evolution is supported by at least as much evidence as is the germ theory of disease--heaps of it, and from many areas of biology. So why is it contemptible to reject germ theory but socially acceptable to reject evolutionary theory?

One answer is religion. Unlike germ theory, the idea of evolution strikes at the heart of human ego, suggesting that we were not the special object of God's attention but were made by the same blind and mindless process of natural selection that also built ferns, fish and rabbits. Another answer is ignorance: most Americans are simply unaware of the multifarious evidence that makes evolution more than "just a theory," and don't even realize that a scientific theory is far more than idle speculation.
Coyne just published Why evolution is true, a book with similar intent, namely to explain evolution as not only true in fact but a true theory as well—at least so far as any scientific can be pronounced true.

Nonetheless Coyne is very complimentary to Dawkins. He spends a lot of time repeating some of the evidence and giving Dawkins credit for explaining it well.

Dawkins describes selection as an "improbability pump," for over time the competition among genes can yield amazingly complex and extraordinary species. Here's how he describes the evolution of tigers:
A tiger's DNA is also a "duplicate me" program, but it contains an almost fantastically large digression as an essential part of the efficient execution of its fundamental message. That digression is a tiger, complete with fangs, claws, running muscles, stalking and pouncing instincts. The tiger's DNA says, "Duplicate me by the round-about route of building a tiger first."
Only Dawkins could describe a tiger as just one way DNA has devised to make more of itself. And that is why he is famous: absolute scientific accuracy expressed with the wonder of a child--a very smart child.
In one passage Coyne discusses the evidence for evolution that comes
from the "bad designs" of animals and plants, which, Dawkins observes, look nothing like de novo creations of an efficient celestial engineer. His favorite example--and mine--is the recurrent laryngeal nerve, which runs from the brain to the larynx. In mammals it doesn't take the direct route (a matter of a few inches) but makes a curiously long detour, running from the head to the heart, looping around the aorta and then doubling back up to the neck. In the giraffe, this detour involves traversing that enormous neck twice--adding about fifteen feet of superfluous nerve. Anyone who's dissected an animal in biology class will surely agree with Dawkins's conclusion: "the overwhelming impression you get from surveying any part of the innards of a large animal is that it is a mess! Not only would a designer never have made a mistake like that nervous detour; a decent designer would never have perpetuated anything of the shambles that is the criss-crossing maze of arteries, veins, nerves, intestines, wads of fat and muscle, mesenteries and more."
(The real reason I started writing this blog post was to quote that paragraph!)

Coyne goes on to discuss Fodor, and Piattelli-Palmarini' What Darwin got wrong. Coyne, like every other review I've seen of this book, is puzzled by how F&P (as he refers to them) could have gone so far wrong. To take just one example,
F&P claim, for example, that selection could never produce winged pigs because of developmental constraints: "Pigs don't have wings because there is no place on pigs to put them. There are all sorts of ways you'd have to change a pig if you wanted to add wings. You'd have to do something to its weight, and its shape, and its musculature, and its nervous system, and its bones; to say nothing of retrofitting feathers."

Haven't F&P heard of bats? Bats evolved from small four-legged mammals, probably resembling shrews. You could say the same thing about shrewlike beasts that F&P did about pigs: how could they possibly evolve wings? And yet they did: selection simply retooled the forelegs into wings, along with modifying the animal's weight, shape, musculature, nervous system and bones for flying (no feathers needed). One of the great joys of being a biologist is learning about the many species in nature whose evolution would appear, a priori, impossible.
I don't know anything about Piattelli-Palmarini, but from my reading of Fodor it seems to me that he wants to say outrageous things almost for the sake of being outrageous. Fodor is a colorful and forceful writer. He presents himself as wanting to appear reasonable while confidently exploring ideas others would fear to investigate. Well he is certainly doing that in this book. But in this case, he seems to have stepped out of his area of competence—and using philosphical tools to attack evolutionary biology just doesn't get very far.

Coyne's own explanation of how F&P got to where they are in this book is the following.
I've pondered long and hard how two thoughtful intellectuals could go so wrong. Behind much of F&P's animus toward natural selection, it seems, is their disdain for evolutionary psychology. …

But evolutionary psychology is a red herring here. F&P are surely entitled to criticize evolutionary psychology, and evolutionary psychologists may be expected to reply. Motivations aside, F&P's attempt to undermine evolutionary biology is a quixotic and misguided undertaking. Their claim to have nullified 150 years of science, and one of humanity's proudest intellectual achievements, with some verbal legerdemain, is not only breathtakingly arrogant but willfully ignorant of modern biology. In the end, F&P's contrarian efforts are all belied by the world of Richard Dawkins--the flourishing field of modern evolutionary biology, where natural selection remains the only explanation for the wondrous adaptive complexity of organisms.

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