The peopling of the Americas marks a major expansion of humans across the planet. However, questions regarding the timing and mechanisms of this dispersal remain, and the previously accepted model (termed ‘Clovis-first’)—suggesting that the first inhabitants of the Americas were linked with the Clovis tradition, a complex marked by distinctive fluted lithic points1—has been effectively refuted. Here we analyse chronometric data from 42 North American and Beringian archaeological sites using a Bayesian age modelling approach, and use the resulting chronological framework to elucidate spatiotemporal patterns of human dispersal. We then integrate these patterns with the available genetic and climatic evidence. The data obtained show that humans were probably present before, during and immediately after the Last Glacial Maximum (about 26.5–19 thousand years ago)2,3 but that more widespread occupation began during a period of abrupt warming, Greenland Interstadial 1 (about 14.7–12.9 thousand years before ad 2000)4. We also identify the near-synchronous commencement of Beringian, Clovis and Western Stemmed cultural traditions, and an overlap of each with the last dates for the appearance of 18 now-extinct faunal genera. Our analysis suggests that the widespread expansion of humans through North America was a key factor in the extinction of large terrestrial mammals.
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The data that support the findings of this study are available in the Article and its Supplementary Information.
Code for OxCal is noted in the Supplementary Information.
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Without implying their agreement with the content of this article, we thank E. Jacob, G. Wali, J. Swift, C. Bronk Ramsey, J. Lee-Thorp, K. Graf and K. Douka for their feedback on versions of the manuscript. We are grateful to the staff of the Oxford Radiocarbon Accelerator Unit, University of Oxford. Funding was provided by the Clarendon Fund Scholarship, University of Oxford.
The authors declare no competing interests.
Peer review information Nature thanks Loren G. Davis, Christopher L. Hill and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.
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Extended data figures and tables
Extended Data Fig. 1 Bayesian age model and start boundary for the Beringian tradition (14,955–13,895 cal. bp).
Right, estimate rounded to 50. Outlier analysis output (O) is noted as ‘posterior probability/prior probability’. δ18O data are according to the Greenland ice-core timescale (GICC05)20.
Extended Data Fig. 2 Bayesian age model and start boundary for the Western Stemmed tradition (14,860–13,065 cal. bp).
Outlier analysis output (O) is noted as ‘posterior probability/prior probability’. δ18O data are according to the Greenland ice-core timescale (GICC05)20.
Extended Data Fig. 3 Bayesian age model and start boundary for Clovis tradition (14,210–13,495 cal. bp).
Outlier analysis output (O) is noted as ‘posterior probability/prior probability’. δ18O data are according to the Greenland ice core timescale (GICC05)20.
Extended Data Fig. 4 Spatio-temporal slices of chronometric data belonging to the cultural components analysed, with a spatial KDE analysis.
a–f, Coloured circles (following colour scheme in Fig. 1) denote chronometric data (n = 387 dates) and white outlines reflect the spatial KDE analysis. Chronometric data were summarized using a KDE_Model analysis (Methods). For each date, differences in circle size reflect increasing or decreasing probabilities at a 95.4% confidence interval. The spatial KDE analysis shows a marked increase in the frequency and distribution of the data immediately, before and during GI-1.
This Supplementary Information file contains a description of the archaeological traditions discussed, information on the archaeological sites included in the analyses and notes on their Bayesian age modelling (including OxCal code), data tabulations tables (S1 and S2), a brief discussion on excluded archaeological sites, and the results of sensitivity testing and ‘Difference’ queries. Readers are guided by a hyperlinked Table of Contents, at the beginning of the document.
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Becerra-Valdivia, L., Higham, T. The timing and effect of the earliest human arrivals in North America. Nature (2020). https://doi.org/10.1038/s41586-020-2491-6