Equines originated between 60 and 50 million years ago with the cocker spaniel-sized Eohippus, or Dawn Horse. This had four padded toes on the front legs and three on the back, which allowed easy movement over wet ground. Eohippus browsed on the leaves of low-growing shrubs and lived in the semi-tropical forests of the U.S. Midwest.
Eohippus evolved to be taller and heavier, with teeth that allowed it to eat a wider variety of plants. The front feet were reduced to three toes.
About 26 million years ago, the horse moved out of the forests and swamps and onto the plains. Its neck and head became longer, the incisors moved forward in the skull and the form and position of the eyes altered to allow the horse to view the horizon while grazing. Its legs became longer, giving it speed to escape from predators and it stood on a single toe.
Equus caballus, which evolved almost two million years ago, was the first true horse. It moved across the Bering Strait from America to Asia. Primitive man followed horse herds back across the Bering Strait into America, some staying to become the first Americans. When the glaciers retreated ten thousand years ago, the land bridges between what is now Alaska and Asia disappeared. Soon after that the horse became extinct in North America. They were later re-introduced to the continent by Spanish explorers, giving rise to the feral Mustang.
The indigenous peoples of the Americas did not have a specific word for horses, and referred to them as a type of dog or deer (in one case, "elk-dog").
Horses were first domesticated as draft animals on the Eurasian Steppe between 4500 and 2500 BC, as people adopted a nomadic way of life and needed an animal to carry their belongings. The horse came to provide transportation, milk, meat and skins. By 1000 B.C., domestication had spread through Europe, Asia and North Africa.
The first record of riding comes from Persia in the third millennium BC. By 1580 BC the innovation had spread to Egypt, and 250 years later it was found in Greece. The first horse training book, the Kikkuli Text, was written in 1360 BC.
The founder of modern horsemanship was the Greek soldier and writer, Xenophon (c.430-354 BC). From the Persians he learned "leg up" mounting - a groundsman would help the rider mount the horse by holding the rider's leg and boosting him up. From the Armenians, he learned to tie pieces of cloth onto his horses' feet to protect them from ice and rocks. After his retirement, Xenophon wrote the definitive book on horsemanship, which is still used, in modern form, by trainers today. He is sometimes described as the "original horse whisperer".
There are several well-known horse whisperers - or people using natural horsemanship methods to great effect - including Monty Roberts, Pat Parelli and Mark Rashid. Their methods vary, but commonly use horse psychology and body language to train horses in a non-abusive manner.