These intelligent, emotional and intuitive animals have survived as a species for tens of thousands of years. Even though they are prey animals and basically "food" for other predatory carnivores they have survived. They became adept at reading the intent and emotion of their predators and,used their speed and agility to avoid hungry predators. About 7,000 years ago they connected with humans in a higher order relationship that saw them also transporting humans and their goods from one place to another, and helping humans work their fields and carry logs to build their homes. And, I'm sure, that on those long winter nights, when all the work was done, there were a lot of "heart to heart" talks had by the pioneer men and women with their horses. They told their dreams, their hopes and their fears to these wonderful beasts with an enormous capacity for listening and responding in just the right way.
From a May 16, 2014 article by Jiffy Read in Stories from the Heart:
"Horses help us feel connected. We're happiest when we feel connected, but the hurts we've experienced in our lives often create a sense of pain and distrust that makes us reluctiant to lower our guard and let others fully in. Horses seek connection. Being connected to a herd in the wild was their best bet for survival. As such, they're wired to connect with us. And because horses don't peddle in guilt or shame like humans do, we feel safe opening ourselvels to a connection with horses."