Here’s an idea presented at YouTube that got kicked around at an ID-friendly online chips n’ gravy fest:
The animal must be able to breed in captivity and must have a social structure in which a human can substitute for an animal. Domesticable animals are rare simply because the combination of necessary features is rare. A human can become the leader of a herd or pack.
Note: Domestic cats, like Tom, Dick and Harry (UD editorial assistants) are not herd or pack animals; However, handled by humans early enough, cats tend to put the human in the role of Mommy Cat. That is, they never really grow up. But that hardly matters if they have found a human who will cater to their needs and neuroses. It is why cats are so numerous on every continent.