• "Beringian" Standstill

Since there has been some confusion between media reports and our recent PNAS article (Tackney et al. 2016), I want to clarify the nature of our arguments with respect to the Beringian Standstill Model.

This model has several elements that have varying genetic and archaeological support. It posits a several thousand-year period of isolation and genetic differentiation in Beringia before a southward dispersal of this population. Recent estimates (by Raghavan et al 2015) suggest this isolation began no earlier than 23,000 years ago and lasted no longer than 8000 years (~15,000 years ago). The model requires ONLY that ancestral Native Americans were genetically isolated from other Asian populations - the location of this isolation remains unknown.

Our data, indicating two distinct haplogroups represented in a single ancient Beringian population (C1b, B2), along with the diversity of other ancient North American samples (see figure) are consistent with the expectations of the Beringian Standstill model (substantial interior Beringian genetic variation in the Late Pleistocene).

However, the genetic data cannot alone identify the geographic location of these early populations. There is no unequivocal archaeological evidence of human occupation in northwest North America before ~14,500 cal BP. We suspect the location of the isolated population (23,000-15,000 cal BP) occurred in northeast Asia, where there is substantial evidence of human occupation during this period.

In sum, our new genomic data support some aspects of the Beringian Standstill model but not others.

All ancient human remains samples with mtDNA analysis (image: Ben A. Potter, UAF)

For more details see:

Tackney, Justin, Ben A. Potter, Jennifer Raff, Michael Powers, Scott Watkins, Derek Warner, Joshua D. Reuther, Joel D. Irish, and Dennis H. O’Rourke

2015    Ancient DNA analyses from Terminal Pleistocene Burials in Eastern Beringia. Proceedings of the National Academy of Sciences. Early Edition, October 26, 2015.