Coyne on Natural Selection

Posted by jrosenhouse on April 27, 2010
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If for some incomprehensible reason you are not interested in the big chess match, and are looking for something evolutiony to read, let me suggest Jerry Coyne’s big review of the recent books by RIchard Dawkins and Jerry Fodor and Massimo Piatelli-Palmarini. The review was published in The Nation. Here’s a nugget:

Indeed, virtually none of the biologists who study the “constraints” described by F&P share their dim view of natural selection. That’s because, over and over again, selection has wrought the most improbable and unpredictable changes in animals and plants. 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.

Go read the whole thing!

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  1. #1 frog
    April 27, 2010

    Seriously? Analogizing a small generalist with a much larger and to some extent more specialized animal?

    Has a pig-level animal ever evolved flight? We know 2 cases of flight evolving in small generalists. I’m not sure about the root stock of pteranodons — but I’d be willing to bet that their first fliers were also small generalists.

    Bats are a terrible example. Coyne should at least go for cetacean evolution — the root was bigger and less general than a shrew. But the question is the other way — how difficult is it to go from marine-adapted swimmer to land-adapted flyer? How often does one happen or the other?

  2. #2 Hansen
    April 27, 2010

    I suspect the authors chose pigs to play a pun on the when pigs fly saying.

  3. #3 frog
    April 28, 2010

    Yeah — that still doesn’t change that the article is TERRIBLE. F&P don’t screw up because they overload constraints — they screw up because nothing they say is new, innovative, or terribly surprising. The limits of constraints are well-known, and don’t say a great deal about how evolution drives biology.

    Here’s another line: if there really were so many constraints on selection, and if development really were so complex and tightly interconnected that organisms could not respond to natural selection, then why would artificial selection be so effective at changing animals and plants?

    That’s just plain dumb. Artificial selection is so effective because we choose organisms that respond the best to our selective pressures. Dogs are a very plastic species, for example. On the other side, we see maize which took millenia to select for sufficient plasticity. It was sucky — and still is pretty sucky — compared to other domesticated plants.

    Coyne & FP are arguing poorly (using metaphorical language) over ancient disputes that were settled long ago. It only confuses the matter to make this kind of “popularization”.

  4. #4 Lenoxus
    April 30, 2010

    When people refer to “flying pigs”, they almost always mean “pigs with bird wings extending from the shoulderblades”, not “Flying creatures with distant porcine ancestors”. Otherwise dolphins could be considered “swimming ungulates” (or swimming shrew-things, for that matter).

    That’s why “retrofitting feathers” is (just) one issue.

  5. #5 Collin Brendemuehl
    May 17, 2010

    I’m reading through F&P right now.
    Interesting, what Coyne did in the article is exactly what F&P predicted at the beginning of the book– he answered with an optimized/idealized example and avoided the difficult questions.