Abstract
Palaeoenvironmental records from the now-submerged Bering Land Bridge (BLB) covering the Last Glacial Maximum (LGM) to the present are needed to document changing environments and connections with the dispersal of humans into North America. Moreover, terrestrially based records of environmental changes are needed in close proximity to the re-establishment of circulation between Pacific and Atlantic Oceans following the end of the last glaciation to test palaeo-climate models for the high latitudes. We present the first terrestrial temperature and hydrologic reconstructions from the LGM to the present from the BLB's south-central margin. We find that the timing of the earliest unequivocal human dispersals into Alaska, based on archaeological evidence, corresponds with a shift to warmer/wetter conditions on the BLB between 14 700 and 13 500 years ago associated with the early Bølling/Allerød interstadial (BA). These environmental changes could have provided the impetus for eastward human dispersal at that time, from Western or central Beringia after a protracted human population standstill. Our data indicate substantial climate-induced environmental changes on the BLB since the LGM, which would potentially have had significant influences on megafaunal and human biogeography in the region.
Highlights
Major dispersal events throughout human prehistory have been linked to sea level and other major environmental changes, such as changes in vegetation and moisture [1,2,3]
The palaeoenvironmental reconstruction from Lake Hill extends from 18 500 years ago to the present and provides, for the first time, multiproxy-based evidence from the Bering Land Bridge (BLB) to compare with existing human biogeographic information
The Late Glacial portion of the Lake Hill record reveals a period of relatively warm and wet conditions, based on the chironomid temperature reconstruction, δ18O values, diatom, cladoceran and Equisetum spores, during the Bølling/Allerød (BA—approx. 14 600 to approx. 14 000 years ago) [41] that is bracketed by the cold and dry conditions associated with both Heinrich Stadial 1 (HS1; from 18 500 to approx. 14 600 years ago) and the Younger Dryas (YD; from 12 900 to approx. 11 650 years ago) [41,42,43]
Summary
Major dispersal events throughout human prehistory have been linked to sea level and other major environmental changes, such as changes in vegetation and moisture [1,2,3]. New genetic and archaeological evidence indicate migration of Native American ancestors through Beringia sometime after 16 000 years ago, but the exact timing and specific routes remain unresolved [10,16]. Ancient Beringians, a newly discovered population of Native Americans, radiated from other groups approximately 20 000 years ago and are connected directly with the Denali complex, located throughout Alaska and adjacent regions between 12 500 and 6000 years ago. This population may represent a second migration event after the initial dispersal of humans through Beringia [10]
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