Some crossed the land bridge between North America and Siberia and spread throughout Asia, Europe and Africa at about the first time that Asians came over to North America to become 'Native Americans'!

The Native Americans made the fatal mistake of hunting the remaining horses and camels to extinction, thus handicapping themselves when Europeans showed up thousands of years later with horses.

The Asians, Europeans and Africans in the Old World were smarter, domesticating these animals and breeding better and better versions.