:’) The main advantage to, for example, the auroch, which was (or at least believed to be) the wild species from which modern cattle come, is that they didn’t run needlessly and didn’t care much whether there was a barrier around them so long as the food was available.
Even before domestication, the open range for the animals made it possible to hunt them effectively without necessarily moving around by the season, because they moved by the herd and stayed in areas where their food was. My belief is that meat was so desirable — and the higher protein led to more brain development in utero and in childhood — that fixed communities of hunter-gatherers were the transitional phase between migratory human bands and settled agriculture.
And just small marginal differences between groups would quickly add up. Think of Koreans when Americans first came during the war. They were small, but now Koreans are as big as an average American, though not quite so tasty when bbq’d.