At the end of the Illinoian Glaciation, and the begining of the Sangamon Interglacial, a new creature called man, may have followed the grazing animals across the Bering Land Bridge that formed at that time.  Not much can be known about such people, as they had no lithic technology yet. Very primitive horses may have crossed over from Asia at this time. Here they had few predators and evolved into modern horses. The horse species Equus actually originated here.  Any people that came across at this time had to lack hunting skills because they posed no threat to the developing horse.