It is widely accepted that the earliest settlement of the American continent occurred during the last Ice Age when prehistoric people crossed from what is now Russia into Alaska over the now disappeared land bridge. These early settlers are believed to be ancestors of the modern Native Americans and Inuit. According to a paper released by EurekAlert, a new research by an international team of researchers led by Professor Eske Willerslev, who holds positions both at St John's College, University of Cambridge, UK, and the University of Copenhagen in Denmark, added new details to the accepted theory, making the whole picture a bit more complicated.

The researchers sequenced the full genome of an infant, a girl whose remains were discovered in 2013 at the Upward Sun River archaeological site in Alaska, and whom the local Native community named Xach'itee'aanenh t'eede gay, or Sunrise Child-girl. Even though the child had lived around 11,500 years ago, long after the arrival of first settlers to the continent, her genetic makeup does not have anything in common with either southern or northern lineages of indigenous Americans.

Ancient Beringians, early offspring of Native American ancestors

Called Ancient Beringians, the newly discovered prehistoric people are thought to descend from the same ancestor group as the Northern and Southern Native American tribal groups, yet they have likely separated from their ancestors earlier in their history and later remained isolated from the common, ancestral Native American population.

Their common ancestors are believed to have first emerged as a distinctive tribal group in Northeast Asia around 36,000 years ago, just before the onset of the Last Glacial Maximum. The climate change, which back then was opposite to the global warming, forced them to migrate on foot to Alaska via the then exposed sea floor of the Bering Strait about 20,000 years ago.

The migrants maintained constant contact with their distant relatives back in Asia until around 25,000 years ago when the gene exchange across the strait finally ceased. This relation breakup was likely caused by brutal changes in the climate, when glacier build up in that part of Siberia isolated the Native American ancestral group which was still residing in Beringia, an ancient land which included dry seabeds of the Chukchi Sea, the Bering Sea, the Bering Strait, as well as the adjacent Chukchi and Kamchatka Peninsulas in Russia, and Alaska in the US.

Early Native Americans arrived from Siberia in single wave of migration

Until the new research, the existence of two separate Northern and Southern branches of early Native American peoples has divided academics regarding the pattern of Americas having been originally settled. The new study allowed the team to postulate that the Ancient Beringian people were more closely related to early Native Americans than their Asian and common Eurasian ancestors. According to Jos Victor Moreno-Mayar, from the University of Copenhagen, "It looks as though this Ancient Beringian population was up there, in Alaska, from 20,000 years ago until 11,500 years ago, but they were already distinct from the wider Native American group." Professor Willerslev summarised the study, "We were able to show that people probably entered Alaska before 20,000 years ago. It's the first time that we have had direct genomic evidence that all Native Americans can be traced back to one source population, via a single, founding migration event."