Dogs are the most diverse animals created by the hand of man. Even the fancy pigeon breeds that helped Darwin gain insight into the process of natural selection do not approach them in variety of form. Yet the origins of those forms are, in many cases, obscure. None of the pedigree books that define modern breeds goes back earlier than the mid-19th century. Those breeds, however, are of more than just amateur interest. The closed-book rules of kennel clubs around the world mean that recognised breeds tend to become more and more inbred, exposing genetic defects that outbreeding would cover up. That is bad for dogs, but good for medical science, as Elaine Ostrander, of the Fred Hutchinson Cancer Research Centre, in Seattle, recognised several years ago.
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