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Foxes bred for tamability in a 40-year experiment exhibit remarkable transformations that suggest an interplay between behavioral genetics and development
When scientists ponder how animals came to be domesticated, they almost inevitably wind up thinking about dogs. The dog was probably the first domestic animal, and it is the one in which domestication has progressed the furthest-far enough to turn Canis lupus into Canis familiaris. Evolutionary theorists have long speculated about exactly how dogs' association with human beings may have been linked to their divergence from their wild wolf forebears, a topic that anthropologist Darcy Morey has discussed in some detail in the pages of this magazine (July-August 1994).
As Morey pointed out, debates about the origins of animal domestication tend to focus on "the issue of intentionality"-the extent to which domestication was the result of deliberate human choice. Was domestication actually "self-domestication," the colonization of new ecological niches by animals such as wolves? Or did it result from intentional decisions by human beings? How you answer those questions will determine how you understand the morphological and physiological changes that domestication has brought about-whether as the results of the pressure of natural selection in a new niche, or as deliberately cultivated advantageous traits.
In many ways, though, the question of intentionality is beside the point. Domestication was not a single event but rather a long, complex process. Natural selection and artificial selection may both have operated at different times or even at the same time. For example, even if prehistoric people deliberately set out to domesticate wolves, natural selection would still have been at work. The selective regime may have changed drastically when wolves started living with people, but selective pressure continued regardless of anything Homo sapiens chose to do.
Another problem with the debate over intentionality is that it can overshadow other important questions. For example, in becoming domesticated, animals have undergone a host of changes in morphology, physiology and behavior. What do those changes have in common? Do they stem from a single cause, and if so, what is it? In the case of the dog, Morey identifies one common factor as pedomorphosis, the retention of juvenile traits by adults. Those traits include both morphological ones, such as skulls that are unusually...