Late date of human arrival to North America: Continental scale differences in stratigraphic integrity of pre-13,000 BP archaeological sites

Abstract

By 13,000 BP human populations were present across North America, but the exact date of arrival to the continent, especially areas south of the continental ice sheets, remains unclear. Here we examine patterns in the stratigraphic integrity of early North American sites to gain insight into the timing of first colonization. We begin by modeling stratigraphic mixing of multicomponent archaeological sites to identify signatures of stratigraphic integrity in vertical artifact distributions. From those simulations, we develop a statistic we call the Apparent Stratigraphic Integrity Index (ASI), which we apply to pre- and post-13,000 BP archaeological sites north and south of the continental ice sheets. We find that multiple early Beringian sites dating between 13,000 and 14,200 BP show excellent stratigraphic integrity. Clear signs of discrete and minimally disturbed archaeological components do not appear south of the ice sheets until the Clovis period. These results provide support for a relatively late date of human arrival to the Americas.

Undiscovered bird extinctions obscure the true magnitude of human-driven extinction waves

“…For the Australasia, Nearctic and Neotropic realms, which have better established and later human arrival dates 129 , 130 , compared to the Indo-Malay and Palearctic 131 , we estimated extinction dates based on truncated exponential decays after first human arrival. We used a Clovis-culture human arrival date for the Nearctic 130 , even though there is evidence of earlier human arrival 132 , 133 , as no consensus has been reached among archaeologists about the date of initial human arrival to the Americas (and evidence of human arrival south of the ice sheets is fragmented), but all agree that human populations were distributed across the North American continent by the Clovis period 134 , implying greater human influence at this point. We modelled 75% of extinctions to occur within 2000 years of first human arrival (half-life of 1000 years), based on the extinction chronology of North American Pleistocene mammals 127 , and truncated the exponential distributions so that 100% of extinctions occurred at the 90 th quantile.…”

Taguatagua 3: A new late Pleistocene settlement in a highly suitable lacustrine habitat in central Chile (34°S)

“…Leaving this debate aside, there is a general consensus that, around 14,000–13,000 cal yr BP, several areas of the Americas were populated ([ 4 , 14 , 23 – 26 ], but see [ 27 ]), and it is plausible to speculate about an exploration phase [ 28 ] with even earlier dates. [ 14 ] propose, based on the Summed Calibrated Probability Density of radiocarbon dates, that humans arrived in South America around 15,500 cal yr BP and that the population did not grow significantly until ∼12,500 cal yr BP, following the Antarctic glaciation (see also [ 14 ]).…”

Ice and ocean constraints on early human migrations into North America along the Pacific coast

“…Several North American archaeological sites have produced possible evidence for human occupations during the LGM ( 10 , 15 , 69 , but see contrary opinions in refs. 70 and 71 ). These ages are easier to reconcile with the estimated time frames for genetic separation between Siberian and Beringian populations than the purported pre-LGM sites, but still require that humans entered the Americas prior to substantial regional deglaciation.…”