Four distinct waves of human migration, between 106,000 and 29,000 years ago, appear to be associated with orbital-scale global climate swings

The Great Human Diaspora includes all worldwide migrations of humans, from their original migration(s) out of Africa––across Asia and Europe, from southeast Asia into Australia, and ultimately from northern Asian into the Americas. On the basis of fossil and archaeological evidence, it has been long been hypothesized that exodus of Homo sapiens––out of Africa and into Eurasia between ~50–120 thousand years ago––occurred in several orbitally-paced migration episodes. Crossing vegetated rainy corridors from northeastern Africa into the Arabian Peninsula, and the Levant, and then expanding further into Eurasia, Australia, and the Americas, early Homo sapiens experienced massive time-varying climate and sea level conditions on a variety of time scales.

Until now, it has remained difficult to quantify the effect of glacial and millennial-scale climate variability on early human dispersal and evolution. Authors [see attached] present results from a numerical human-dispersal model, which is forced by spatio-temporal estimates of climate and sea-level changes over the past 125,000 years. The model simulates the overall dispersal of H. sapiens in close agreement with archaeological and fossil data: this model features prominent glacial migration waves across the Arabian Peninsula and the Levant region around 106–94, 89–73, 59–47 and 45–29 thousand years ago.

These findings document that orbital-scale global climate swings played a pivotal role in shaping the Late Pleistocene global population distributions, whereas millennial-scale abrupt climate changes, associated with Dansgaard–Oeschger events, had a more limited and regional effects. [The Dansgaard–Oeschger events (usually abbreviated D–O events) represent “rapid” climate fluctuations––that occurred 25 times during our last Glacial Period. Many climatologists claim that these D-O events occur quasi-periodically with a recurrence time being a multiple of 1,470 years.

Timmermann & Friedrich, Nature  ?? Sept 2o16; 537: doi:10.1038/nature19356 ; deMenocal & Stringer,doi:10.1038/nature19471

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