The first people: the first people on north america were old world hunters who crossed a land bridge (beringia) into alaska and yukon 30,000 years ago. Beringia was a product of the last ice advance, due to a drop in sea level. Beginning 15,000 years ago, the climate warmed, the ice sheets retreated, and the sea level rose, causing beringia to become submerged underwater. People that were still in alaska had to wait until an ice-free corridor appeared 12,000-13,000 years ago before they could migrate into north america. Another possible migration route was island-hopping to the west of the cordillera ice sheet. The first people of north america were called paleo-indian (they developed into three distinct hunting cultures clovis, folsom, plano). Paleo-indians: they were descendants of the old world hunters. These spearheads and woolly mammoth bones have been discovered in the prairies.