Rethinking the timing of the populating of the Americas

The Great Human Diaspora (i.e. “migration of Homo sapiens across the planet, originating originally in Southeast Africa”) has been a part of our evolution theme, often discussed in these GEITP pages. Today’s topic is “peopling of the Americas.” For many years, it was believed that the time of entry of northeastern Asians into what is now Alaska — was thought to coincide with the opening of “an ice-free corridor” ~13,000 years ago (13 kya) between the great northern continental ice sheet (called Laurentide Ice Sheet) and the ice-covered northern Rocky Mountains (the Cordilleran Ice Sheet) in western Canada. An ice-free corridor ~13 kya would also be roughly consistent with the end of Earth’s Last Glacial Period (LGP) — estimated to have occurred from ~115,000 to ~11,500 years ago (115-11.5 kya). This paradigm proposed that, once below the 48th parallel north, these human groups developed a material tradition (named Clovis, after the Clovis, New Mexico archeological site) that spread across North America, and which dates to between 13.25 and 12.8 kya. This narrative, known as the “Clovis-first” model, was widely accepted for most of the 20th century.

More recently, however, many studies have begun to suggest much earlier migrations. Data from sites more than 13 kya in North and South America (first reported in the 1970s), raised the possibility of earlier arrivals. Also, archaeological excavations in Chiquihuite Cave in northern Mexico provided evidence of human occupation ~26.5 kya…!!. This Mexican site now joins half a dozen other documented archaeological sites in northeast and central Brazil that have yielded evidence suggesting dates for human occupation between 20,000 and 30,000 years ago [see the excellent Figure from attached editorial]. Authors [see attached two articles & editorial] report the latest convincing evidence that initial settlements on the American continent happened much earlier (i.e. at least 10,000 years earlier) than has been widely accepted. Studies of radiocarbon dating of early archaeological sites revealed that interior regions of Alaska, Yukon in Canada, and the continental United States were already widely populated before 13 kya.

Authors [see attached two articles] present results of recent excavations at Chiquihuite Cave — that corroborate previous findings in the Americas of cultural evidence that dates to back before the Last Glacial Maximum (LGM) which was 26.5-19 kya. These data push back dates for human dispersal to the region — possibly as early as 33 to 31 kya (33,000–31,000 years ago). The Chiquihuite Cave site yielded about 1,900 stone artefacts within a 3-meter-deep stratified sequence, revealing a previously unknown stone/calculi (lithic) industry that underwent only minor changes over millennia. More than 50 radiocarbon and luminescence dates provided chronological control — and genetic, palaeo-environmental, and chemical — data that document the changing environments in which the occupants lived. These results provide new evidence for the antiquity of humans in the Americas, illustrating the cultural diversity of the earliest dispersal groups, which dramatically predate those of the Clovis culture. 😊


Nature 6 Aug 2020; 584: 87-92, 93-97 & editorial pp 47-49

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