Ancient DNA analysis sheds light on the early peopling of South America

The Americas were the last continent to be inhabited by humans. An increasing body of archaeological and genomic evidence has hinted to a complex settlement process. This is especially true for South America, where unexpected ...

Many unanswered questions still persist, such as whether the first humans migrated south along the Pacific coast or by some other route. While there is archaeological evidence for a north-to-south migration during the initial peopling of the Americas by ancient Indigenous peoples, where these ancient humans went after they arrived has remained elusive. Using DNA from two ancient human individuals unearthed in two different archaeological sites in northeast Brazil—Pedra do Tubarão and Alcobaça—and powerful algorithms and genomic analyses, Florida Atlantic University researchers in collaboration with Emory University have unraveled the deep demographic history of South America at the regional level with some unexpected and surprising results.

Not only do researchers provide new genetic evidence supporting existing archaeological data of the north-to-south migration toward South America, they also have discovered migrations in the opposite direction along the Atlantic coast—for the first time. The work provides the most complete genetic evidence to date for complex ancient Central and South American migration routes. Among the key findings, researchers also have discovered evidence of Neanderthal ancestry within the genomes of ancient individuals from South America. Neanderthals are an extinct population of archaic humans that ranged across Eurasia during the Lower and Middle Paleolithic.

The figure depicts the deep ancestries of the ancient individuals of the Americas and archaic ancestry in ancient South America and Panama. The pie chart radius reflects the proportion of shared archaic ancestry in the individual. Credit: Florida Atlantic University Read more

The first southern North American groups entered South America and spread through the Pacific coast settling the Andes (yellow arrow). At least one population split occurred soon after, branching the first groups that settled the Atlantic coast (green arrow) from the groups that gave rise to the ancient populations of Southern Cone. New Migrations may have then emerged along the Atlantic Coast, with a possible origin around Lagoa Santa, heading north toward Northeast Brazil and Panama, and south to Uruguay. Eventually, Uruguay and Panama were linked by a south-to-north migration route closer to the Atlantic coast (purple double-headed arrow). Credit: Florida Atlantic University Read more

Researchers used teeth from ancient samples collected in archeological sites in northeast Brazil. Teeth are especially important in ancient DNA analysis because of the excellent preservation of biomaterials within the tooth. Credit: Laboratório de Arqueologia Biológica e Forense, Universidade Federal de Pernambuco Read more

The Alcobaça archaeological site, in which the skeletal remains of Brazil-12 (northeast Brazil) were unearthed. Credit: Henry Lavalle, Universidade Federal de Pernambuco and Ana Nascimento, Universidade Federal Rural de Pernambuco Read more