Horses and humans have always had a unique relationship. Ever since ancient times, humans and horses have helped each other survive, and like all other domesticated animals, they still help us with everyday lives today. In fact, there have been accounts of horses (sometimes wild) being attracted to humans knowing that humans would often provide for them. It is kind of amazing that two completely separate species have evolved side by side for so many years and are still an integral part of one another’s’ existence.
The thing about horses and humans is that they are one of the many instances of symbiotic relationships that are still seen today. Dogs for example are another species that have been domesticated from wild animals and are now simply part of human life. Horses and other domesticated animals have gotten to the point where wild horses are sort of a rarity.
Biologically, horses are much different than they were thousands of years ago, and much of this reason is because of being domesticated. Domesticated species have different biology than wild animals, and need much less feral traits in order to survive. And although wild horses still do exist, most are domesticated and much more docile. In time, there may be no wild horses left in the world simply because they are so useful to humans, and say what you want about it, but both species have been crucial to the other species survival. Evolving side by side to make the lives of both species better.