An explanation as to how changes in habitat over millions of years may have caused the modern horse to evolve from an animal no bigger than a fox.
Among the earliest known ancestors of the modern horse (Equus) is Hyracotherium Eohippus, which is believed to have lived around 55 million years ago. The creature was around 60 cm long and weighed 23 kg with four-toed feet and a slender body rather unlike what we would now call a horse. Hyperaesthesia lived in the woodlands of North America and Western Europe during the Eocene era, the hottest period in pre-history. During this time, the ground was mostly soft and moist (particularly in the forest areas), and so the animals were best served by walking with their toes spread out, and their body weight spread evenly between them. This allowed them to walk along soft surfaces without sinking in and becoming stuck.
Eventually the main land became harder and dryer, meaning that the original configuration was no longer necessary (and indeed potentially detrimental). With the ground more stable, the mammals could now run at a much faster pace, so the evolutionary emphasis shifted from buoyancy to power. In order to achieve this, the horses became larger, with their limbs lengthening, and their toes becoming more pointed. With the later generations of the horse now pushing off from one toe, their land speed was dramatically increased, allowing them to more easily outrun predators. There have been other changes, too: with each generation the originally wide-spread toes moved closer together, eventually becoming the now familiar hoof. Meanwhile the teeth changed shape and became more numerous (particularly molars) to keep up with changes in diet.
By the time Homo Sapiens Sapiens developed, the horse had grown to a height of 1.6 metres, and has earned an unofficial title as “Man’s second-best friend” due to their superb pulling and carrying ability making them a vital tool in the formation and development of human civilisation.