You seem to be implying that it's biological. It's not, it's entirely cultural. Non-American women (unless they're highly Americanized) aren't like this at all. Chinese women aren't really big on pets, because people there don't have indoor pets very much. Also, black American women don't have dogs (or cats) very much at all. This is a cultural thing, and so I don't see how you can claim it's some kind of innate biological thing, unless you're going to claim that white American women are biologically different from everyone else in the world.