Most camels surviving today are either domesticated, or feral, having only returned to the wild. Along with all other megafauna but bison in North America, the original wild camels were wiped out during the spread of Native Americans from Asia into North America, 12,000 to 10,000 years ago.
Like the horse, before their extinction in their native land, they spread across the land bridge, moving the opposite direction from the Asian immigration to America, to survive in the Old World and eventually be domesticated and spread globally by humans.
Dromedaries may have first been domesticated by humans in southwestern Arabia, between 6,000 and 3,400 years ago, the bactrian in central Asia 2500 years ago.
