How the first humans came to America remains a mystery. The most widely held theory holds that an ancestral Siberian people crossed the Bering Strait and colonized the entire continent from north to south during the last Würm Ice Age (sometime around 110,000 years ago to around 9700 BC). However, more recent finds suggested a possible earlier conquest. Now, examination of the largest collection of genomic data from Brazil, including the DNA of Luzio, the oldest skeleton found in Sao Paulo, sheds new light on the origins of these early Americans: Luzio, who lived about 10,000 years ago, is a descendant of the ancestral population who settled in the Americas at least 16,000 years ago and produced all of today’s indigenous peoples, including the Tupi, Guarani, or Cherokee. The conclusions have just been published in the journal Nature Ecology & Evolution.
The authors also wanted to explain the reason for the sudden disappearance of the oldest coastal communities that established the so-called “Sambaquis”. Also known as shellfish dumps and common to other coasts around the world, sambaquis are huge mounds of shells and spines that served as a sort of “dump” in which they deposited mostly the hard parts of mollusks, which they mainly used to feed on themselves , but also bone and even pottery.
“After the Andean civilizations, the sambaqui builders of the Atlantic coast were the most densely populated human phenomenon in pre-colonial South America,” explains André Menezes Strauss, an archaeologist at the Museum of Archeology and Ethnology at the University of São Paulo (MAE-USP) and principal investigator on the study. “They were the ‘Kings of the Coast’ for thousands of years. But suddenly they disappeared about 2,000 years ago.”
Reconstructing history from genomes
The authors analyzed the genomes of 34 samples from four different areas of the Brazilian coast. The fossils were at least 10,000 years old and came from Sambaquis and other sites (notably Cabeçuda, Capelinha, Cubatão, Limão, Jabuticabeira II, Palmeiras Xingu, Pedra do Alexandre and Vau Una). Among the human remains are those of the aforementioned Luzio, the oldest skeleton in São Paulo, found in the shell midden of the Capelinha River in the Ribeira de Iguape Valley by a group led by Levy Figuti, a professor at MAE. USP
The morphology of its skull is similar to that of Luzia, the oldest human fossil found in Brazil to date, dating back around 11,400 years. Researchers hypothesized that it may have belonged to a population biologically distinct from modern-day Native Americans, who settled in present-day Brazil about 14,000 years ago. But they were wrong. “Genetic analysis showed that Luzio was Native American, like Tupi, Quechua or Cherokee,” says Strauss. That doesn’t mean they’re all the same, but from a global perspective, they all stem from a single migration wave that reached the Americas no more than 16,000 years ago. If there was another population here 30,000 years ago, it left no descendants among these groups.”
Basically the same, but with differences
Luzio’s DNA also showed that there were two distinct migrations: one inland and one along the coast. Analysis of the genetic material revealed heterogeneous communities with cultural similarities but significant biological differences, particularly between the southeastern and southern coastal communities. “Studies of skull morphology conducted in the 2000s had already indicated a subtle difference between these communities, and our genetic analysis confirmed this,” notes Strauss. “We found that one of the reasons was that these coastal populations were not isolated but were ‘exchanging genes’ with inland communities. This process must have contributed to regional differences among the Sambaquis over millennia.”
Because the sambaquis on the coast were not the same as those inland, near the rivers, although they were similar, proving that there were relationships and contacts between them. Now, ancient DNA also reveals that it was more than just a matter of culture.
Why have the sambaqui builders disappeared?
As for the mysterious disappearance of this coastal civilization, analysis of the DNA samples clearly revealed that it was a change in practices in this part of the world, as opposed to the European Neolithic replacement, which saw entire populations all but “evaporated”. with a decline in the construction of sambaquis and the introduction of pottery. For example, the genetic material found at Galheta IV (Santa Catarina State), the most emblematic site of the period, has ceramic remains, not shell remains, and in this respect resembles the classic sambaquis. That is: they replaced the shell sambaquis with ceramics.
“This information is consistent with a 2014 study that analyzed potsherds of sambaquis and found that the pots in question were not used to cook domesticated vegetables, but were used to cook fish.” appropriated from the interior in order to process traditional foods there,” says Strauss. Other studies have suggested that it was climate change, specifically the drop in sea levels in the Atlantic Ocean that accompanied the decline of these ancient civilizations.