Animal Breeding as Evolution "In Action"?
Ann Gauger's post "Is Evolution Random? Answering a Common Challenge" is an excellent answer to those who still today affirm Darwin's contention that domestic breeding offers an example of evolution "in action." But there is more to say. Alfred Russel Wallace wrote in his famous Ternate letter:
Again, in the domesticated animal all variations have an equal chance of continuance; and those which would decidedly render a wild animal unable to compete with its fellows and continue its existence are no disadvantage whatever in a state of domesticity. Our quickly fattening pigs, short-legged sheep, pouter pigeons, and poodle dogs could never have come into existence in a state of nature, because the very first step towards such inferior forms would have led to the rapid extinction of the race; still less could they now exist in competition with their wild allies. The great speed but slight endurance of the race horse, the unwieldy strength of the ploughman's team, would both be useless in a state of nature. If turned wild on the pampas, such animals would probably soon become extinct, or under favourable circumstances might each lose those extreme qualities which would never be called into action, and in a few generations would revert to a common type, which must be that in which the various powers and faculties are so proportioned to each other as to be best adapted to procure food and secure safety, -- that in which by the full exercise of every part of his organization the animal can alone continue to live. Domestic varieties, when turned wild, must return to something near the type of the original wild stock, or become altogether extinct.
Thus, the selection of domestic breeders (artificial selection) is both quantitatively and qualitatively different from natural selection -- quantitatively because breeder selection is much stronger, and qualitatively because breeder selection is more obviously goal-directed toward things unrelated to fitness. This argument from analogy is, therefore, false on its face. Wallace was right in pointing it out in 1858 and it remains true today.
But there's a further problem. As Bert Theunissen points out in his paper "Darwin and his pigeons. The analogy between artificial and natural selection revisited," Darwin didn't even have a full appreciation of what breeders actually did. Selection is only a broad gloss on the subject. Crossing and inbreeding are also important factors used by conscious breeders in creating domestic animals.
Theunissen notes that Darwin believed most breeds were of ancient origin; they are not. Bottom line: Darwin's analogy simply doesn't work. So while his brand of natural selection may not be considered in an entire and literal sense "random," neither does it involve the kind of careful thought and pre-selection planning of the domestic breeder. Nor is it the sort of blind, random, purposeless, wholly natural causes operating to produce speciation that Darwin himself insisted upon. Darwin himself stated in his Autobiography:
The old argument from design in Nature, as given by Paley, which formerly seemed to me so conclusive, fails, now that the law of natural selection has been discovered. . . . There seems to be no more design in the variability of organic beings, and in the action of natural selection, than in the course which the wind blows.
But there are many more design options than that offered by Paley, and more to the point, domestic breeders don't achieve their purposes by the whimsy of the wind either.
This matters for two reasons. First, because the argument from breeding was extremely important to Darwin. His first two chapters in Origin are devoted to it. As Jean Gayon has argued in Darwin's Struggle for Survival:
The use of the domestic analogy was not a pedagogic device. It was methodological essential, without it, the subtle interrelationship between variation, heredity and modification, so characteristic of the Darwinian hypothesis of selection, would have been nothing more than empty speculation without any empirical content.
Second, it matters because it demonstrates how different the respective evolutionary theories of Charles Darwin and Alfred Russel Wallace really were. Darwin was interested in individual competition leading to variation, while Wallace was concerned more broadly with competition and variation within a biogeographical context of group dynamics. On Darwin's behalf it should be said that such significant differences between the two need to be carefully considered by those leveling charges of plagiarism or a "Darwin conspiracy" theory.
Image credit: B. Schoener (Self-photographed) [Public domain], via Wikimedia Commons.