Pleistocene 2,000,000 to 12,000 ya: several ice ages in the pleistocene. Most recent ice age: weichsel glaciation (wisconsin in north america) ca. 115,000 - 12,000 ya: alternating periods of extreme cold (glaciers advance) and warming (glaciers melt, most recent advance 20,000 - 12,000 ya. During ice age, much water remains on land, in form of ice, and is removed from the. Ice thickness in southern ontario around 20,000 years ago. A sense of scale? oceans: 2000 meters. Glaciers push out and kills off plants, animals, fish which lived in the area: change the conditions for human adaptation. Ocean level drops, exposing ocean bed as dry land: land bridges form between continents (sunda, sahul, beringia) Major influence on human populations: http://www. youtube. com/watch?v=t9nw66rcmhg. First nations perspectives: have occupied the land since mythological times ( time immemorial ) Archaeology / biological anthropology: most evidence points to an origin in northeastern asia. Possibly a common ancestor with the modern ainu and kitchak peoples of.