Beringia and the global dispersal of modern humans

Abstract

Until recently, the settlement of the Americas seemed largely divorced from the out-of-Africa dispersal of anatomically modern humans, which began at least 50,000 years ago. Native Americans were thought to represent a small subset of the Eurasian population that migrated to the Western Hemisphere less than 15,000 years ago. Archeological discoveries since 2000 reveal, however, that Homo sapiens occupied the high-latitude region between Northeast Asia and northwest North America (that is, Beringia) before 30,000 years ago and the Last Glacial Maximum (LGM). The settlement of Beringia now appears to have been part of modern human dispersal in northern Eurasia. A 2007 model, the Beringian Standstill Hypothesis, which is based on analysis of mitochondrial DNA (mtDNA) in living people, derives Native Americans from a population that occupied Beringia during the LGM. The model suggests a parallel between ancestral Native Americans and modern human populations that retreated to refugia in other parts of the world during the arid LGM. It is supported by evidence of comparatively mild climates and rich biota in south-central Beringia at this time (30,000-15,000 years ago). These and other developments suggest that the settlement of the Americas may be integrated with the global dispersal of modern humans.

Earliest Human Presence in North America Dated to the Last Glacial Maximum: New Radiocarbon Dates from Bluefish Caves, Canada

“…32,000 cal BP [14, 15], the Bluefish Caves site proves that people were in Eastern Beringia during the LGM, by at least 24,000 cal BP, thus providing long-awaited archaeological support for the “Beringian standstill hypothesis”. According to this hypothesis, a human population genetically isolated existed in Beringia from about 15,000 to 23,000 cal BP [9], or possibly earlier [3–5, 10], before dispersing into North and eventually South America after the LGM [3–12,77–79]. …”

“…Central Beringia may have sustained human populations during the LGM since it offered relatively humid, warmer conditions and the presence of woody shrubs and occasional trees that could be used for fuel [12, 33, 37]. However, this putative core region was submerged at the end of the Pleistocene by rising sea levels making data collection difficult.…”

“…Bluefish Caves, situated in Eastern Beringia, may have been located at the easternmost extent of the standstill population’s geographical range. The seasonal movements of human hunters from a core range, hypothetically located in Central Beringia, into adjoining, more steppic regions such as Eastern Beringia would explain the sporadic nature of the occupations at Bluefish Caves [12]. …”

“…18,000–24,000 cal BP) where they were genetically isolated for up to 8,000 years before moving south of the ice-sheets into North America [3–11]. Unfortunately, archaeological support for the standstill hypothesis is scarce [12]. Recent archaeological discoveries prove that humans were able to adapt to high-latitude, Arctic environments by at least 45,000 cal BP [13].…”

Is theory about peopling of the Americas a bridge too far?

“…During that cold and arid period, Beringia's most productive ecosystem was the area now just offshore of southern Alaska, according to modeling of the ancient vegetation based on local temperatures, carbon-dioxide levels, and other conditions. Ice-age sediment drilled from the nearby sea floor included pollen from birch and alder (9). Unless that pollen eroded out of older sediments, it indicates relatively mild conditions, says paleoecologist Nancy Bigelow of the University of Alaska Fairbanks.…”