Study dismantles theory of settlement of Americas
Brazilian natives are now said to stem from a single ancestral group
Published on 15/11/2018 - 13:09 By Camila Maciel - São Paulo
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The theory according to which the Americas were originally populated by two migration waves from Northeast Asia—with a population carrying African and Australian traits, and another with Amerindians similar to present-day indigenous—has just been disproved.
A study based on fossil DNA has analyzed samples from the oldest skeletons found in the continent, and confirms the existence of a single ancestral group for all ethnic groups in America.
The discovery led to a redesign of the strikingly African-looking face of Luzia—as the skull was the Paleoamerican young woman found in the 1970s in Brazil is referred to.
The conclusion is based on the research conducted by 72 scientists from eight countries, including scholars from the University of São Paulo (USP), Harvard University, and Max Planck Institute, in Germany.
Archaeogenetic data reveal that all populations in America stem from a single group that arrived in the New World through the Bering Strait some 20 thousand years ago.
The DNA links this migration flow to peoples in Siberia and northern China. The results of the research were published Thursday (Nov. 8) in scientific magazine Cell.
Luzia, who lived in Lagoa Santa, Minas Gerais state, 12,500 years ago, had her face reconstructed for the first time by British scholar Richard Neave.
Her features were based on a theory by University of São Paulo (USP) Professor Walter Neves, according to which the people of Luzia—the set of fossils found in the 19th century in Minas Gerais—arrived before the ancestors of present-day indigenous people in Brazil.
The first migration wave, therefore, is believed to have had African or Australian traits. The thesis was based on a morphological analysis of the skull, which indicated that these people were considerably different from present-day natives.
Archaeologist André Menezes Strauss, at the USP Archaeology and Ethnology Museum, who coordinated the Brazilian part of the study, explains that Neves’s contribution was key to ascertaining there were differences between the ancestral and modern-day indigenous individuals, but genetic studies—aided by today’s technology—refute his thesis, which argues that this difference was brought about during the process of migration between continents.
“This link with a previous population of Africa did not exist. The difference between Lagoa Santa and current natives originated in America itself,” he declared.
Luzia’s new face was designed by Caroline Wilkinson, from Liverpool John Moores University, UK, a specialist in forensic reconstruction and a follower of Neave.
The descendants of the ancestral migratory wave that came down south through North America split into two lineages some 16 thousand years ago.
The members of one of the lineages crossed the Isthmus of Panama and peopled South America on three different occasions.
The first was between 15 and 11 thousand years ago; the second wave 9 thousand at the most. The study shows the presence of fossil DNA from both contingents throughout the South American continent. The third migration wave is the most recent one—some 4.2 thousand years back—and settled chiefly in the central Andes region.
The genetic data reveal that Luzia’s people had strong ties with the Clovis culture, a lineage of human beings who went south from the north approximately 16 thousand years back.
It was hitherto not known that this group had migrated south. This group, however, was short-lived.
“It started dying out some 9 thousand years ago, and was replaced with the direct ancestors of the indigenous groups that lived in Brazil during the colonial period,” the study says. The reasons that led to the disappearance of the Clovis groups remain unknown.
Strauss explains that the new archaeogenetic technique brings information previously inaccessible to archaeologists.
“It opens up a world of analytical possibilities, not just for determining ancestral relations, miscegenation, and sex, but also for ascertaining kinship, investigating phenotype, diseases, metagenomics—countless studies and information now made available,” he pointed out.
He further reports that these technological strides were made in the past ten years or so, especially thanks to the work of Max Planck Institute, which has revolutionized archaeological studies.
As for the Lagoa Santa fossils, one of the challenges was DNA extraction, as the tropical climate speeds up the deterioration of the genetic material.
“We made the first modest attempts in 2012. It wasn’t working at first, so it took us at least two years until we were familiar with the protocol for DNA extraction that worked for Lagoa Santa,” he recounted.
The German institute, however, had managed to extract the Neanderthal DNA in 2010. Of the 49 individuals analyzed, seven skeletons aged 10.1 thousand to 9.1 thousand years originated from Lapa do Santo, a rocky shelter in Lagoa Santa.
Fossils found in Argentina, Belize, Chile, and Peru were also used—adding up to 15 archaeological sites.
Strauss says that the next steps will include increasing DNA samples in a bid to understand the process of settlement of the Americas in further detail.
“[We’re working to] find other groups, other archaeological sites and skeletons, from which we may extract genetic material to ascertain exactly when this population arrived as well as their relation with other groups,” he explained.
An archaeogenetics laboratory is expected to be built at USP in 2019. “We hope it may become a center attracting Latin American colleagues so they can carry out analysis here, in collaboration with peers from Europe and the US,” the expert said.
Nearly a hundred skulls excavated by Neves and Strauss over the last 15 years are stored at USP. Other fossils are kept at the Pontifical Catholic University of Minas Gerais.
However, according to São Paulo Research Foundation FAPESP, which provides funding for excavation campaigns, most of this archaeological archive was kept in Rio de Janeiro’s National Museum, consumed by a fire on September 2 this year.
Luzia’s skull was being displayed in the museum next to a bust with its features by Neave. The representation of the original face was lost in the fire, but copies had been made. Luckily, fragments of the skull were salvaged from the rubble.
The piece is among the oldest fossils ever found in the American continent. “[Confirming] what has been observed in the 12 skeletons scrutinized—which is considerable—is just natural. Nearly all of them point in the same direction, so we assume Luzia should follow suit. Of course, we can’t be sure, if we can’t examine the fossil,” Strauss stated.
He reported that the DNA must be extracted from the fragments of Luzia’s skull recovered from the fire after permission is granted by the museum.
“The material was exposed to extremely high temperatures and if there’s something that DNA doesn’t take kindly to is heat, as it shatters the material to pieces. We have to keep expectations modest,” he concluded.
Translation: Fabrício Ferreira - Edition: Kleber Sampaio / Nira Foster