Analysis of ancient and present-day genetic samples from California and Canada identified a similar DNA ancestry. This suggests possible "reconvergence" between two separated ancient populations.
The result of the analysis suggested that there were two ancient populations that separated between 15,000 and 18,000 years ago: the southern branch and the northern branch.
The two populations lived apart and reproduced their respective northern and southern descendants. These descendants meet again at some point and produced another lineage that could possibly be the first Americans.
If the analysis is accurate, it would mean that all native populations in North, Central, and South America shared a genetic ancestry from a northern ancient population that is most closely related to the indigenous people of eastern Canada.
The present study, conducted by researchers from the universities of Cambridge in the United Kingdom and Illinois Urbana-Champaign in the United States, thereby challenges previous findings that a population who migrated to the south had solely given rise to people in Central and South America.
The study published in the journal Science also challenges the findings that the first humans to reach North America took a land bridge, which previously connected Alaska and Siberia before wandering south through an "iceless" corridor that opened up during the end of the last ice age.
The present study is leaning toward a more recent theory that the first Americans instead used an ancient Pacific coastal route to reach North America.
Northern And Southern Branch
The analysis of ancient genetic samples from southwest Ontario revealed that after the divergence of this ancient population, the indigenous ancestors who gave rise to the northern branch migrated to the Great Lakes regions. Their migration may have been made possible by the melting glacial regions during the last wave of the Ice Age.
Meanwhile, the southern branch continued with their migration down the Pacific coast, residing on the islands that they saw along the way. Indeed, the prehistoric population associated with the Clovis culture of 13,000 years ago had been found to have originated from the people of the southern branch.
The stone relics of the Clovis culture were first discovered in Clovis, New Mexico. Clovis people were first thought to be the sole ancestors of Native Americans.
However, the current genetic study found that present-day Central and South American populations possessed traces of about 42 percent to as high as 71 percent of the genes coming from the northern branch.
Furthermore, the present genetic analysis found that population in Southern Chile, in the same area as the Monte Verde or the oldest known human settlements in the Americas, possessed the highest proportion of the genes similar to that of the northern branch.
"It was previously thought that South Americans, and indeed most Native Americans, derived from one ancestry related to the Clovis people," highlighted Dr. Toomas Kivisild, co-senior author of the study.
"We now find that all native populations in North, Central and South America also draw genetic ancestry from a northern branch most closely related to Indigenous peoples of eastern Canada."
The team said that they have yet to pinpoint exactly the timing of when the actual historic reconvergence between the southern and northern branch took place.
The blending of the lineage may have occurred either in North America prior to expansion south or as people continued to migrate deeper into the southern continent, tracing the western coast down.
It could also be that there had been several reconvergences between the two ancient populations that all occurred around 13,000 years ago.