Belayev with his foxes as they turn tame and doglike

These dog-like features were side-effects. Belyaev and his team did not deliberately breed for them, only for tameness. Those other dog-like characteristics seemingly rode on the evolutionary coattails of the genes for tameness. To geneticists, this is not surprising. They recognize a widespread phenomenon called 'pleiotropy', whereby genes have more than one effect, seemingly unconnected. The stress is on the word 'seemingly'. Embryonic development is a complicated business. As we learn more about the details, that 'seemingly unconnected' turns into 'connected by a route that we now understand, but didn't before'. Presumably genes for floppy ears and piebald coats are pleiotropically linked to genes for tameness, in foxes as well as in dogs. This illustrates a generally important point about evolution. When you notice a characteristic of an animal and ask what its Darwinian survival value is, you may be asking the wrong question. It could be that the characteristic you have picked out is not the one that matters. It may have 'come along for the ride', dragged along in evolution by some other characteristic to which it is pleiotropically linked.

The evolution of the dog, then, if Coppinger is right, was not just a matter of artificial selection, but a complicated mixture of natural selection (which predominated in the early stages of domestication) and artificial selection (which came to the fore more recently). The transition would have been seamless, which again goes to emphasize the similarity - as Darwin recognized - between artificial and natural selection.

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