Late Glacial Maximum - North America

North America

Over the land between the Lena Basin and northwest Canada, increased aridity occurred during the Last Glacial Maximum. Sea level fell to about 120 m below its present position, exposing a dry plain between Chukotka and Western Alaska. Clear skies reduced precipitation, and loess deposition promoted well-drained, nutrient-rich soils that supported diverse steppic plant communities and herds of large grazing mammals. The wet tundra soils and spruce bogs that exist today were absent. Cold temperatures and massive ice sheets covered most of Canada and the northwest coast, thus preventing human colonization of North America prior to 16,000 years ago. An "ice free corridor" through western Canada to the northern plains is thought to have opened up no earlier than 13,500 years ago. However, deglaciation in the Pacific northwest may have taken place more rapidly and a coastal route could have been available by 17,000 years ago. Rising temperatures and increased moisture accelerated environmental change after 14,000 years ago, as shrub tundra replaced dry steppe in many parts of Beringia.

Camp settlement sites are found along Tanana River in central Alaska by 14,000 years ago and some evidence suggests human exploration at the Bluefish Caves in the Yukon as early as 15,500 years ago. Earliest occupation levels at the Tanana Valley sites contain artifacts similar to the Siberian Dyuktai culture. At Swan Point, these comprise micoblades, burins, and flakes struck from bifacial tools. Artifacts at the nearby site of Broken Mammoth are few, but include several rods of mammoth ivory. The diet was of large mammals and birds, as indicated by fauna remains. Earliest site occupation at Ushki sites of central Kamchatka (ca. 13,000 years ago) display evidence of small oval houses and bifacial points. Stone pendants, beads, and a burial pit are present. In central Alaska up the northern foothills at the Dry Creek site ca 13,500-13,000 years ago near Nenana Valley, small bifacial points were found. It is thought that people moved into this area to hunt elk and sheep on a seasonal basis. Microblade sites typologically similar to Dyuktai appear ca 13,000 years ago in central Kamchatka and throughout many parts of Alaska.

Around 12,000 years ago, the rising sea level reached a position less than 60 metres below today's level and flooded the lowlands between Chukotka and western Alaska. The ensuing increase in moisture accelerated Alaska's transition to wet tundra and coniferous forests. The Bering Land Bridge had closed and thus Beringia ceased to exist. At about this time, sites that comprise the Denali complex appeared and persisted to ca. 7,500 years ago. Denali complex sites indicate high yields of caribou remains ca. 8,000 years ago and corresponds with an increase in settlement size.