Too small at the time, it took a concerted breeding program for ancient steppe peoples to first breed horses able to pull chariots, and then big enough to be ridden.

Humans have been migrating over the world for tens of thousands of years and yet the horse was first able to be used for transportation about 4 thousand years ago.

https://www.nps.gov/articles/000/ancient-horse.htm#:~:text=Equus scotti had a close,or hoof%2C like modern horses.