An international group of researchers, including Prof. Alan Cooper from the Environment Institute & Director of the Australian Centre for Ancient DNA (ACAD), have uncovered remarkable details about the population history of Central and South America
Recently published in the journal Cell, two previously unknown genetic exchanges between North and South America have been revealed. The genomes of 49 individuals from Central and South Americas were analysed, some as old as 11,000 years, and compared to modern genomes from the Americas and across the globe. Buried ancient human remains were analysed after consultation with indigenous communities and government agencies. Previous to this study, the oldest genomes analysed from this region were 1,000 years old.
|This individual from the site of Los Rieles in Chile is the oldest in the study at ~11,000 years ago. Photo credit: Bernardita Ladrón de Guevara, 2008|
Link between a Clovis culture-associated individual and the oldest Central and South American
The results provide new insights into the early history of the area. A distinctive DNA type, associated with the first widespread archaeological culture of North America (Clovis), was found in Chile, Brazil and Belize 11, 000- 9000 years ago. “This supports the hypothesis that the expansion of people who spread the Clovis culture in North America also reached Central and South America,” explains co-lead author Cosimo Posth of the Max Planck Institute for the Science of Human History.
Intriguingly, ancient individuals less than 9000 years old and present-day individuals from South Americans did not share the Colvis culture-associated ancestry. “This is our second key discovery: we have shown that there was a continent-wide population replacement that began at least 9,000 years ago,” Says co-senior author David Reich from Harvard Medical School and the Howard Hughes Medical Institute.
After the population turn-over, there was striking genetic continuity between ancient individuals dating to up to 9,000 years ago and modern people from multiple South American regions. This contrasts with West Eurasia and Africa where there are few places with such long-standing continuity.
|Graphic showing the geographic movement of populations discussed in the study. Photo credit: Graphic: Michelle O’Reilly; Posth, Nakatsuka et al. 2018. Reconstructing the Deep Population History of Central and South America. Cell.|
California Channel Island-associated ancestry in the Andes
A second distinctive shared ancestry was discovered between ancient Californians from the Channel island and the community that became widespread in southern Peruvian Andes, at least 4,200 years ago. The connection between these regions has been hypothesised as a result of spreads of people thousands of years earlier rather than a spread specifically from Channel Islands into South America.
“It could be that this ancestry arrived in South America thousands of years before and we simply don’t have earlier individuals showing it. There is archaeological evidence that the population in the Central Andes area greatly expanded after around 5,000 years ago. Spreads of particular subgroups during these events may be why we detect this ancestry afterward,” said Nathan Nakatsuka of Harvard Medical School, co-lead author of the study.
The future of ancient DNA research in the Americas
Researchers stress that this population history picture is far from complete, but they are a glimpse of the discoveries yet to come. Researchers recognised the limitations in the availability of the ancient data from different regions and individuals dating before 11,000 years ago. “We lacked ancient data from Amazonia, northern South America and the Caribbean, and thus cannot determine how individuals in these regions relate to the ones we analysed,” explained Reich.
However, researchers are excited by the future potential. “With future, regionally focused studies with large sample sizes, we could realise the potential of ancient DNA to reveal how the human diversity of this region came to be the way it is today,” states co-senior author Johannes Krause of the Max Planck Institute for the Science of Human History.
Read more about this study here.