Abstract
Scandinavia was one of the last geographic areas in Europe to become habitable for
humans after the Last Glacial Maximum (LGM). However, the routes and genetic composition
of these postglacial migrants remain unclear. We sequenced the genomes, up to 57×
coverage, of seven hunter-gatherers excavated across Scandinavia and dated from 9,500±
6,000 years before present (BP). Surprisingly, among the Scandinavian Mesolithic individuals,
the genetic data display an east±west genetic gradient that opposes the pattern seen in
other parts of Mesolithic Europe. Our results suggest two different early postglacial migrations
into Scandinavia: initially from the south, and later, from the northeast. The latter followed
the ice-free Norwegian north Atlantic coast, along which novel and advanced
pressure-blade stone-tool techniques may have spread. These two groups met and mixed
in Scandinavia, creating a genetically diverse population, which shows patterns of genetic
adaptation to high latitude environments. These potential adaptations include high frequencies
of low pigmentation variants and a gene region associated with physical performance,
which shows strong continuity into modern-day northern Europeans.