In the course of selective breeding of the silver fox, an initiative undertaken by Belyaev, it was demonstrated that the character of the wild fox over the course of several generations gave way to increasing amenability to domestication, or tamability; that is, a reduction in the wild nature of this animal (e.g., aggression and fear) (Belyaev, 1969; Trut, 1999) and the emergence of behavioral features that make this animal more social in its relation to humans.
Early canid domestication: The farm-fox experiment: Foxes bred for tamability in a 40-year experiment exhibit remarkable transformations that suggest an interplay between behavioral genetics and development.