The first largescale study of ancient DNA from early American people has reconstructed a genetic history of Indigenous American populations, confirming the devastating impact of European colonisation.
Led by University of Adelaide's Australian Centre for Ancient DNA, the researchers examined DNA from 92 pre-Columbian mummies and skeletons, between 500 and 8600 years old. Their paper published in Science Advances, provides the first real time genetic record of when and how the Americas were populated.
None of the pre-Columbian genetic lineages revealed in the ancient humans were found present in modern Indigenous Americans.
This suggests that the separation of the examined lineages from today's Indigenous populations was established as early as 9000 years ago.
And it suggests that the pre-Columbian genetic lineages became extinct with the arrival of the Spaniards.
According to the authors, the most plausible scenario is that shortly after the initial colonisation populations established that stayed geographically isolated from one another. A major portion of these later became extinct following European contact.
This would also closely match the historical reports of a major demographic collapse immediately after the Spaniards arrived in the late 1400s.
The study's findings also provide a more precise timing of the first people entering the Americas - confirming that it occurred around 16,000 years ago via the Beringian land bridge that connected Asia and the north-western tip of North America during the last Ice Age.
With the limited resources available, and cold deserts and ice sheets blocking human movement, the founding populations were small, limiting the genetic diversity in these early people.
But they then spread southward remarkably swiftly, reaching southern Chile by 14,600 years ago.