Domestication is a whole different matter than taming. Taming is training a single animal. Subsaharian Africans were not ''dumber'' than other cultures-they domesticated the local bovines well enough as well as dogs.
But certain species are fit for domestications and others are not-dogs were domesticated from either grey wolves or the immediate ancestor of grey wolves, not hyenas or foxes. Likewise, the auroch was relatively easy to domesticate, the bison was not. (It's sort of domesticated right now, but it involve large grazing areas and substantial issues compared to normal cattle-so much issues that most ''early'' society would not have cared)