The nature of horses : exploring equine evolution, intelligence, and behavior
Peta people should read this book. It is a bit "dry" in places but I found it fascinating. It says the dog and horse in a sense chose to be domesticated. Their personalities evolved to fit in with humans and that saved them from extinction. A lot of species have mutually beneficial relationships. If it was us, the humans, who picked which species were domesticated then why can't we tame other wild animals? Yes, some can be to a point but you cannot train a gazelle like you can a horse for example. Most horses, dogs and cats have found a pretty good niche by throwing their lot in with humans. Nature in the wild can be pretty cruel.