Re: Zebras and Unhappy Marriages: A serious discussion, 2
To start things off, here's a theory (read: guess): large mammals in Eurasia become more "civilized", as far as animals go, having more complex "societies" that manage to co-exist without conflict (hierarchical, overlapping, temperament). These are very much "civilized" traits, in that they directly facilitate animals living at higher densities - which is how we ourselves live, in a civilization, and how we want our domesticable animals to live. Aggressive traits, such as head-butting in the mating season, are a waste of expensive resources.
A precondition for these to evolve is some benefit, which here is the advantage of numbers for protection, and greater numbers also enables them to spread and out-compete other species. Evolution also requires support for higher densities, which comes from Eurasia (particularly the Fertile Crescent) being fertile and able to support large numbers. Evolution is helped by time, numbers and diversity - the long east-west shape of Eurasia gives many habitats at similar latitudes, making a larger "test tube" for evolution; and the number of niches within that gives diversity. There's a coincidence here, that faster maturation enables faster evolution of these traits, which also is convenient for further evolution by us (i.e. domestication).If this theory is correct, animals in other regions would tend to also evolve towards these herding traits and temperaments. i.e. I'm seeing it as a parallel to our own civilization (which we might well call our own "domestication" - *we* ourselves were a domesticable species).
EDIT: found an essay on point: http://www.pbs.org/gunsgermssteel/variables/zebra.html
It claims that because zebras evolved alongside humans, they are wary of us; whereas large mammals in other regions were tame. This lead to the extinction of large mammals at human hands in Australia and America - why not in Eurasia too? This doesn't explain their generally antisocial behaviour, which is also directed to their herd-fellows, and not specifically reserved for human beings http://www.africa-wildlife-detective.com/zebras.html;
and their wariness would be related to the many predators in Africa, not just humans.
IDEA: perhaps those herds in Eurasia were also in an expanding phase filling an empty habitat, rather than a crowded competitive arena like Africa? Like a business in a new field, it succeeds by telling people about it and getting them to try it; but in a mature industry, it's a nasty zero-sum game). I don't know if Eurasia *was* empty - except that at that time (13,000 BC), an ice age was just ending, opening and expanding ecological niches. Whatever animals could fill them fastest would win.