Dna mutations dating migrations lesson
The lowered sea level, and an isostatic bulge equilibrated with the depression beneath the Cordilleran Ice Sheet, exposed the continental shelf to form a coastal plain.
While much of the coastal plain was covered with piedmont glaciers, unglaciated refugia supporting terrestrial mammals have been identified on Haida Gwaii, Prince of Wales Island, and outer islands of the Alexander Archipelago.
The oxygen isotope record from the Greenland Ice Cap suggests that these cycles after about 45k years BP lasted anywhere from hundreds to between one and two thousand years, with greater duration of cold periods starting around 32k cal years BP.
The abandonment of the northern regions of Siberia due to rapid cooling or the retreat of game species with the onset of the LGM has been proposed to explain the lack of archaeosites in that region dating to the LGM.
Ongoing research reconstructing Beringian paleogeography during deglaciation could change that estimate and possible earlier submergence could further constrain models of human migration into North America.
These populations expanded south of the Laurentide Ice Sheet and rapidly throughout both North and South America, by 14,000 years ago.
The Buttermilk Creek Complex in Texas, 40 miles northwest of Austin, is seen as one of the oldest confirmed sites in the Americas, dating to 15,500 years ago.
It features the oldest spear points in the Americas.
Indigenous peoples of the Americas have been linked to Siberian populations by linguistic factors, the distribution of blood types, and in genetic composition as reflected by molecular data, such as DNA.
The "Clovis first theory" refers to the 1950s hypothesis that the Clovis culture represents the earliest human presence in the Americas, beginning about 13,000 years ago; evidence of pre-Clovis cultures has accumulated since 2000, pushing back the possible date of the first peopling of the Americas to about 13,200–15,500 years ago.