Ancient Beringian

• 1. Introduction

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  At the Upward Sun River site, an infant who died 11,500 years ago left behind the genome that defines a lineage called Ancient Beringian. Researchers labeled the remains USR1. No population living in Alaska today carries this lineage forward. That absence is the puzzle this documentary sets out to trace. Where did the Ancient Beringian lineage begin, and how did it vanish from Alaska's population history?

• 2. Origins In Beringia

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  Geneticists trace the earliest layer to a population called pre-Ancestral Native American. It split from the East Asian lineage sometime after 36,000 years ago, with gene flow continuing until about 25,000 years ago.

  Between 25,000 and 20,000 years ago, this population mixed substantially with a separate lineage called Ancient North Eurasian. The research describes that Eurasian lineage as the result of a palaeolithic admixture between ancient West Eurasians and ancient East Eurasians. The resulting blend, roughly 65 percent East Asian and 35 percent Ancient North Eurasian, formed the Ancestral Native American lineage by 20,000 years ago. Geneticists say this pattern fits a model in which people crossed into the Americas by way of Beringia during the Last Glacial Maximum.

  The Ancient Beringian lineage broke away from Ancestral Native American at about the same 20,000-year mark. It then persisted in Alaska largely on its own, without significant further admixture, for roughly the next 8,000 years. That same branching, dated to roughly 20,000 to 18,000 years ago, also produced the ancestors of other Paleo-Indian populations across the Americas. That split's consequences would later reach back into Alaska itself.

• 3. The Upward Sun River Find

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  In 2013, excavators recovered the remains of two female infants at the Upward Sun River site, evidence that would carry the Ancient Beringian lineage's name. The site is affiliated with the Denali Complex, a dispersed archaeological culture found across the American Arctic.

  Scientists carried out the genomic analysis of the older infant's nuclear DNA, the sample known as USR1. The work took place at the Centre for Geogenetics, part of the University of Copenhagen's Natural History Museum of Denmark.

  The team published its results in January 2018, in the scientific journal Nature. The comparison set the infant's genome against a wide range of both ancient and present-day genomes. That same comparison is what let the 2018 study trace what came after Ancient Beringian in Alaska's population history.

• 4. Extinction And Replacement

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  A 2018 study concluded that the Ancient Beringian lineage is extinct, with no trace of it in Alaska's living indigenous populations. The researchers suggest Ancient Beringian was replaced, or absorbed, by a back-migration of a population called North Native American, or NNA, into Alaska.

  Modern Athabaskan populations descend from a mixture of that NNA back-migration and a separate Paleo-Siberian lineage. The research dates that blend to before about 2,500 years ago.

  Between 17,500 and 14,600 years ago, that Paleo-Indian branch split further into North Native American and South Native American lineages. That split reflects the dispersal that carried early populations across the Americas, the same movement whose branches would, generations later, send migrants back into Alaska.