EOCENE to PLEISTOCENE PERIOD: 48 million - 10,000 years ago
The ancestry of the modern horse, Equus, can be first traced back to the Eocene Period 60 million years go to a little multi-toed horse-like creature not any larger than a fox. This earliest of horse was a flexible and likely very nimble animal that ran on five-toed feet. Over a period of tens of millions of years, several species developed and the body size of the horse increased and became more robust. The feet developed then into three-toed limbs and eventually, horses with a single hoof emerged. Domestication of the horse has led to a dizzying array of breeds but none that resemble what the prehistoric horses would have exactly looked like. There is one surviving species, though. The Przewalski's Horse is the last surviving wild horse species and cave paintings in France made by Upper Paleolithic humans exactly resemble this beautiful and unique creature as they exist today.