Ancient South Americans Have Neanderthal & Denisovan DNA
Some of the oldest humans on the continent's genetic origins are being revealed by two archaeological sites in Brazil.
The existence of DNA from extinct human species such as Neanderthals and Denisovans has been found by researchers studying the genomes of ancient South Americans. The report was published this week in the Proceedings of the Royal Society B1. The study, which examined ancient genomes from skeletal remains from Brazil, Panama, and Uruguay, also revealed the early South Americans' transcontinental travel habits. Neanderthal or Denisovan ancestry has never before been linked to ancient South Americans, which is what makes this study remarkable.
In the most recent research, the scientists compared the genomes of prehistoric human remains discovered in South America with prehistoric remains discovered all over the North America. Their samples included remains from Alaska, as a surrogate to ancient Beringia. The study also used two ancient entire genomes that were recently sequenced from teeth discovered in northeast Brazil.
The scientists also compared modern genomes from throughout the world and DNA sequences from Denisovan and Neanderthal bones from Russia in addition to the ancient human genomes that were the focus of the analysis. The team's investigation shows that some of the human bones are only 1,000 years old, in contrast to the latter remnants, which date back across tens of thousands of years (Neanderthals vanish from the fossil record approximately 40,000 years ago).
The authors estimated that these interbreeding experiences between anatomically modern humans and Neanderthals and Denisovans likely taken place millennia before the first human populations arrived in the Americas through Beringia, which can account for the presence of these ancestries in ancient Native American genomes. However, it also showed that migrations happened in the opposite way, along the Atlantic coast. The findings confirmed archaeological evidence of north-to-south migration toward South America.
The investigation also discovered Australasian signals in the remains of one individual from Panama and portions of Neanderthal and Denisovan DNA in the ancient South American genomes, which is perhaps the most exciting finding. The Australasian signal, which is still present in the Sirui people of Amazonia, was earlier found in ancient ruins in southeast Brazil. Strangely, the additional Denisovan ancestry seen in some populations does seem to correspond with additional Papuan ancestry. Future research should determine precisely when this Australasian ancestry component first occurs in the Americas and how much Denisovan/Neanderthal ancestry it brings with it.
More Denisovan ancestry was detected in the genomes of the prehistoric people from Panama and Brazil than Neanderthal-specific ancestry. Nowadays, people all around the world are the opposite. To put it another way, the majority of us are more Neanderthal than Denisovan. As far back as 40,000 years ago, South American humans were admixed with Denisovan lineage, and the remnants of a 1,500-year-old person from Uruguay still showed signs of this. Early North American skeletons show no signs of the Australasian signal, indicating that ancient Australasians may have reached the Americas without crossing Beringia. In order to do that, the team plans to study more contemporary and historic Native American and Polynesian genomes in the future research.
The lack of a distinct pattern in the purported Australasian ancestry in the Americas, which has been found in isolated samples that have been separated by great distances in time and space, is puzzling. Such ancestors may have traveled via a non-Beringian route—Austronesians were skilled navigators—during their migrations across the Pacific.
The genetics of extinct hominin species are increasingly influencing how we understand the history of humankind. As more ancient genomes are analyzed, researchers will be able to create a more full picture of how humans spread across the continents and how much of what makes us human truly comes from species other than Homo sapiens.
Campelo Dos Santos, A. L., Owings, A., Sullasi, H. S. L., Gokcumen, O., DeGiorgio, M., & Lindo, J. (2022). Genomic evidence for ancient human migration routes along South America’s Atlantic coast. Proceedings. Biological Sciences, 289(1986), 20221078. https://doi.org/10.1098/rspb.2022.1078