Isn't it crazy that horses have been around 45-55 million years and they used to be multi-toed instead of having one single hoof!
WHAT? NO WAY! I did not know that!  
Yeah pretty nuts! Humans only started domesticating them too around 4000BC
In any part of the world specifically?
That I'm actually not too sure of, but I would assume Mesopotamia because that's where most humans were around that time I think. So modern day Iraq maybe? Correct me if I'm wrong
Ok, and are there different breeds of horses?  
There are hundreds! They divide horses into three different categories. Hot bloods, cold bloods, and warmbloods.