Recommend “Guns, Germs and Steel” for a treatment on the domestication of animals. The author makes a distinction between animals that are “tame” and those that are “domesticated”. Both can be approached/trained, but only the “domesticated” are reared by humans through selective breeding.
So his theory fits nicely with this article in that there was a long ‘association’ of “tame” wolf-dogs with humans before the animals were “domesticated”. The change in status probably occured when humans developed fixed farming communities and/or mobile herding communities.
By that definition, the many varieties of snake morphs being created should be considered domesticated animals.
:)