CAMBRIDGE, MASSACHUSETTS — A new study can now finally explain how and why horses evolved from having toes to hooves.
The New York Times reports that equines such as horses and zebras are unique for being the only living animals with only one toe on each foot. But this wasn't always the case.
The earliest horses were small and lived in forests, with four digits on their front legs and three on the back. Their side toes were essential, and helped carry their body weight.
As their habitat transitioned from forest to grassland, horses' bodies grew larger and their side toes started to shrink. To compensate for the extra load, the middle toe bone became thicker and more robust.
Transitioning to a single toe may have also made it easier for the animals to run farther and faster.
The study, published in the Proceedings of the Royal Society B examined fossilized bones of ancient horses and used computer simulation to determine how the bone structures bore the animals' weight.
