So, a long time ago, there were these animals called Eohippus. They were tiny little creatures, about the size of a small dog. They had short legs and 4 toes on their front feet and 3 toes on their back feet.
Over time, Eohippus evolved into other animals, like Mesohippus and Miohippus. These animals got bigger and taller, and their legs got longer. They also started to lose some toes – Mesohippus had 3 toes on their front feet and 3 on their back feet, while Miohippus only had 3 toes on their front feet and 1 toe on their back feet.
Then came along the genus Equus, which includes horses, zebras, and donkeys. Equus horses have just one toe on each foot, which is pretty different from their ancestors who had lots of toes. They also have long legs and strong muscles, which help them run fast.
So basically, over time, horses got bigger, their legs got longer, and they lost some toes. This all helped them survive in their environment and become the horses we know today!