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Researchers have analyzed sediment core from a lake located in the northern foothills of Alaska’s Brooks Range to investigate the Beringian standstill hypothesis (BSH) of human migration into the Americas.
As the final land mass to be colonized by Homo sapiens, the Americas represent a major landmark in the history of mankind, the fulfilment of a journey from near extinction to world colonization, and the successful accession to evolutionary dominance across the globe. However, the timeline and pathway of that arrival remain a contentious issue even after decades of debate (1,2,3).
At the heart of the issue lies the Beringia, the corridor of human migration to the Americas, which appeared between eastern Siberia and the western edge of the Laurentide ice sheet during the last ice age. The traditional theory posits a “swift peopling” of the Americas via the Bering land bridge from Asia. However, more recent genetic data and archaeological finds have challenged this view.
The alternative theory is known as the Beringian standstill hypothesis (BSH), in which a population of proto-Americans migrated from Asia during or even prior to the point in time when glacial ice sheets were at their largest. The period of separation is the crucial part of this theory with evidence of thousands of years of isolation needed to prove the BSH theory to be viable (4,5).
Archaeological, genetic, and paleoenvironmental evidence so far has offered complementary, but also conflicting timelines, with the lack of direct physical evidence of human occupation in eastern Beringia being a major obstacle to determining the timing and manner of human migration to the Americas (1,6).
In an attempt to correct this evidential deficit, researchers analyzed sediment core from a lake located in the northern foothills of Alaska’s Brooks Range. The lake is located on an older glacial landscape that escaped glaciation during the last ice age, allowing it to archive environmental changes from that time period.
Sediment core samples were obtained from the lake and analyzed using traditional paleoecological methods to analyze charcoal and pollen, and gas chromatography–mass spectrometry (GC–MS) to analyze polycyclic aromatic hydrocarbons (PAHs) and sterols. Transient climate model simulations were then used to contextualize the findings and the ecological interpretations (7).
Results support the theory of human presence in the region. This was demonstrated by the existence of faecal biomarkers, and evidence of elevated burning during the period, which suggests human ignition as a likely culprit.
The data indicate that humans occupied eastern Beringia at the same time they inhabited Siberia, and they affected the Arctic landscapes during the height of the last ice age, confirming the theory that founder populations of the Americas were present in the Arctic regions well before full expansion into the Americas occurred.