How the first humans arrived in the Americas remains a mystery. The most widely accepted theory is that an ancient Siberian people crossed the Bering Strait during the last Würm Ice Age (sometime between about 110,000 years ago and around 9700 BC), colonizing the entire continent from north to south. However, recent discoveries pointed to a possible earlier conquest. Now, the study of the largest amount of genomic data from Brazil, including the DNA of Luzio, the oldest skeleton found in São Paulo, sheds new light on the origins of these first Americans: Luzio, who lived about 10,000 years ago, was a descendant of the ancestral population that settled in the Americas at least 16,000 years ago and gave rise to all present-day indigenous peoples, including the Tupi, Guaraní, and Cherokee. The findings have just been published in the journal Nature Ecology & Evolution. The authors also wanted to explain the reason behind the sudden disappearance of the oldest coastal communities, which built the so-called "sambaquis." Also known as concheros (shell middens) and found on other coasts around the world, sambaquis are enormous mounds of shells and spines that were used as a kind of "garbage dump," where they deposited mainly the hard parts of mollusks, which these people primarily ate, but also bones and even pottery. "After the Andean civilizations, the sambaqui builders of the Atlantic coast were the human phenomenon with the highest population density in pre-colonial South America," explains André Menezes Strauss, archaeologist at the Museum of Archaeology and Ethnology of the University of São Paulo (MAE-USP) and principal investigator of the study. "They were the 'kings of the coast' for thousands and thousands of years. But suddenly, they disappeared about 2,000 years ago." Reconstructing History Through Genomes The authors analyzed the genomes of 34 samples from four different areas along the Brazilian coast. The fossils were at least 10,000 years old and came from sambaquis and other sites (specifically, Cabeçuda, Capelinha, Cubatão, Limão, Jabuticabeira II, Palmeiras Xingu, Pedra do Alexandre, and Vau Una). Among the human remains, those of the aforementioned Luzio, the oldest skeleton in São Paulo, were found in the Capelinha River shell midden in the Ribeira de Iguape Valley by a group led by Levy Figuti, a professor at MAE-USP. Related News standard No The two oldest known families discovered: up to seven generations without a trace of infidelity Judith de Jorge Two family trees created from the DNA of 94 individuals from a French necropolis shed light on the way of life and relationships of a Neolithic community from 6,700 years ago The morphology of her skull is similar to that of Luzia, the oldest human fossil found to date in Brazil, dated around 11,400 years ago. Researchers thought she might have belonged to a biologically different population than today's Native Americans, who settled in what is now Brazil around 14,000 years ago. But they were wrong. "Genetic analysis showed that Luzio was Amerindian, like the Tupi, the Quechua or the Cherokee," says Strauss. That doesn't mean they're all the same, but from a global perspective, they all derive from a single migratory wave that arrived in 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." Similar in basis, but with differences Luzio's DNA also revealed 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, especially between the southeastern and southern coastal communities. "Cranial morphology studies conducted in the 2000s had already pointed to a subtle difference between these communities, and our genetic analysis confirmed this," Strauss notes. "We discovered that one of the reasons was that these coastal populations were not isolated but 'exchanged genes' with inland communities. Over thousands of years, this process must have contributed to the regional differences among the Sambaquis." Because the coastal sambaquis were not the same as those inland, near the rivers, although they were similar, proving that there were relationships and contact between them. Now, ancient DNA also reveals that it was more than a cultural issue. Why did the sambaqui builders disappear? Regarding the mysterious disappearance of this coastal civilization, analysis of DNA samples clearly revealed that, in contrast to the European Neolithic replacement, in which entire populations almost "evaporated," what happened in this part of the world was a change in practices, with a decline in sambaqui construction and the introduction of ceramics. For example, the genetic material found in Galheta IV (Santa Catarina state), the most emblematic site of the period, does not have remains of shells but of ceramics and is similar to classic sambaquis in this respect. That is, they replaced the shell sambaquis with ceramic ones. MORE INFORMATION news No This was the reentry of the European satellite Aeolus: a historic end to a pioneering mission news No Hubble detects a planet with hiccups "This information is compatible with a 2014 study that analyzed ceramic fragments from sambaquis and found that the pots in question were not used to cook domesticated vegetables but fish. They appropriated technology from the interior to process foods that were already traditional there," notes Strauss. Other studies have suggested that it was climate change, specifically the drop in sea level in the Atlantic Ocean, that brought about the decline of these ancient civilizations.
