The Peopling of the Americas

During the Last Glacial Maximum, roughly 26,500 to 19,000 years ago, sea levels stood as much as 120 meters lower than today, exposing a broad landmass, up to 1,000 kilometers wide, connecting Siberia and Alaska across what is now the Bering Strait. This region, known as Beringia, supported a steppe-tundra ecosystem sometimes called the "mammoth steppe," capable of sustaining human populations. Genetic research by Erika Tamm and colleagues (2007, PLOS ONE) proposed the "Beringian standstill hypothesis": that the ancestral population of Native Americans remained genetically isolated within Beringia for several thousand years, roughly between 25,000 and 15,000 years ago, developing distinctive founding mitochondrial lineages before subsequently expanding into the Americas proper.