An international team of researchers has revealed unexpected details about the peopling of Central and South America by studying the first high quality ancient DNA data from those regions.
The findings suggest that the people who spread the Clovis culture, the first widespread archaeological culture of North America, had a major demographic impact further south than previously appreciated.
The authors analyzed genome-wide data from 49 individuals from Central and South America, some as old as 1
Ved at sammenligne gamle og moderne genomes fra Amerika og andre dele af verden, var forskerne i stand til to obtain qualitatively new insights into the early history of Central and South America.
Published in the journal Cell the study was led by researchers at Harvard Medical School; the Howard Hughes Medical Institute; The Max Planck Institute for the Science of Human History; the University of California, Santa Cruz; Pennsylvania State University; the University of New Mexico; The University of Sao Paulo and other institutions in Argentina, Australia, Belize, Brazil, Chile, the European Union, Peru and the United States.
The researchers obtained official permits to execute and conduct analysis on ancient human remains and consulted with local governmental agencies and indigenous communities.
Clovis link in the oldest Central and South Americans
A distinctive DNA type associated with the Clovis culture was found in Chile, Brazil and Belize 11,000 to 9,000 years ago.
"A key discovery was that a Clovis culture-associated individual from North America dating to around 12,800 years ago shares distinctive ancestry with the oldest Chilean, Brazilian and Belizean individuals," said co-lead author Cosimo Posth of the Max Planck Institute for the Science of Human History. "This supports the hypothesis that the expansion of people who spread the Clovis culture in North America also reached Central and South America."
However, the Clovis culture-associated lineage is missing in present-day South Americans and in ancient samples that are less than 9,000 years old.
"This is our second key discovery," said co-senior author David Reich, professor of genetics at Harvard Medical School and a Howard Hughes Medical Institute investigator. "We have shown that there was a continent-wide population replacement that began at least 9,000 years ago."
After the population replacement, there was striking genetic continuity between ancient individuals dating 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.
California Channel Island-Associated Ancestry in the Andes
The second previously unknown spread of people revealed itself in an analysis showing that ancient Californians from the Channel Islands have a distinctive shared ancestry with groups that became widespread in the southern Peruvian Andes by at least 4,200 years ago.
The researchers say this is unlikely to reflect population spread specifically from the Channel Islands into South America. Instead, they hypothesize that the connection between these regions is the result of expansions of people that occurred thousands of years earlier, and that such ancestry became more widespread in the Andes after subsequent events within South America.
"It could be that this ancestry arrived in South America thousands of years before and we simply did not have earlier individuals showing it, "said Nathan Nakatsuka, a research assistant in the Reich lab at Harvard Medical School and co-lead author of the study. "Der er arkæologiske bevis på at befolkningen i det centrale Andes-området i stor grad blev udvidet efter omkring 5.000 år siden. Spred af bestemte undergrupper under disse begivenheder kan være, hvorfor vi opdager dette forfædre bagefter."
Loven om gammel DNA-forskning in the Americas
The researchers emphasize that their study gives only a glimpse of the discoveries that may come through future work.
To learn about the initial movements of people into Central and South America, they say, it
"We lacked ancient data for the period between 11,000 and 3,000 years ago. This study focused on, the picture is far from complete.
from Amazon, North America and the Caribbean, and thus can not determine how individuals in these regions relate to those we analyzed, "said Reich. "Filling in these gaps should be a priority for future work."
"We are excited about the potential of research in this area," said co-senior author Johannes Krause of the Max Planck Institute for the Science of Human History. "Med fremtidige regionalt fokuserte studier med store stikstørrelser, kunne vi realisere det potentiale af gammelt DNA for at afsløre, hvordan den menneskelige mangfoldighed i denne region kom til at være den måde det er i dag."
First peoples: Study finds two ancient ancestries 'reconverged' with settling of South America
Cell, Posth et al .: "Reconstructing the Deep Population History of Central and South America" DOI: 10.1016 / j.cell.2018.10.027, https://www.cell.com/cell/fulltext/S0092-8674(18 ) 31380-1