That issue is addressed by the co-evolution clause, which posits that the ancestors of modern Zebras underwent selective pressure for hostility and avoidance towards the ancestors of modern humans as the latter became more dangerous. (Note that the use of 'ancestor' here does not assume any position on whether these ancestors were a different species than their current descendants.)

I get that. It explains why the dodo was fearless, and all the american animals.

We ate all of them when we showed up, in the american case c. 10000BC, long before iron weapons.

My point is that if the wild horses we first met were similarly tame, then surely we would have eaten them too. We didn’t. So probably they weren’t.

So that can’t be what stopped us domesticating african animals.

Maybe what made Asian horses somewhat wary of Homo Sapiens when they showed up was their experience with previous migrations of hominids (Homo Erectus, Denisovans, Neanderthals). This would assume that these predecessors were less dangerous to horses than were the early humans in America, possibly because they were less widely or more thinly spread, or dispersed more slowly.

I believe Jared Diamond answers this question in Guns, Germs and Steel. Africans didn't have iron tools and were not as effective hunters, so the animals had a much longer time to adapt against their predators.

Perhaps when you're not such a good hunter, you tend more to use whatever you can catch for food. When you're an expert hunter, you start to think about other possibilities.

Or we ate them to massive multiplication and huge success (chicken, cows, pigs, goats, ducks, turkeys, sheeps...)