Sambaqui communities (a word for ‘shell mounds’) were founded. about 8,000 to 1,000 years ago along a stretch of more than 3,000 kilometers on the east coast of South America. According to archaeological records, the sambaqui builders shared clear cultural similarities. However, contrary to what was expected, these groups of people possessed significant genetic differences.
This is suggested by an international research group, led by the University of Tübingen and the Brazilian University of São Paulo, with CIDEGENT researcher Domingo C. Salazar, of the Universitat de València, who compiled the largest set of genomic data in Brazil to demonstrate that the Sambaqui communities on the south and southeast coasts did not constitute a genetically homogeneous population.
On the Atlantic coast of Brazil, drifts several hundred meters long and occasionally more than thirty meters high can be found. “These cultural relics, known as ‘sambaquis’, were raised during a period of 7,000 years”, explains the first author, Tiago Ferraz.
These constructions “consist mainly of shells and other daily debris that they fossilized over time”, says Ferraz. The sambaquis were used by the ancient indigenous peoples “as a dwelling, cemetery and territorial delimitation, and are among archaeological phenomena more charming than precolonial South America”, Add. The sambaqui have always been built in a similar way over a long period of time, over a large area, while the associated communities shared cultural similarities.
“To clarify the population history of indigenous societies on the east coast of South America, we generated data from complete genome of 34 individuals from four regions different from Brazilthat were up to 10,000 years old,” says lead author, paleontropologist André Strauss, of the Museum of Archeology and Ethnology of the University of São Paulo.
“These data include genomic information from ‘Luzio’, a skeleton found in a sambaqui river called the Capelinha. Is considered the oldest evidence of presence human in southeast Brazil,” Strauss points out.
In the research paper, the researchers show that early Holocene hunter-gatherers were genetically distinct from each other and from later populations living in eastern South America. This suggests it there were no direct reports with groups then coastal. The team’s analyzes also indicate that contemporary sambaqui groups from the southeastern coast of Brazil on the one hand and the southern coast of Brazil on the other were genetically heterogeneous.
According to the study, the intensification of contacts between inland and coastal populations about 2,200 years ago was accompanied by a marked decline in construction From piles of shells. During the same period, important environmental changes took place. Strontium isotope analysis has also shown that it is precisely at this time that non-local individuals in the archaeological record.
The isotope ratios of the element strontium are fixed on tooth enamel formed during childhood, which represent the values of the underlying geological area in which the individual lived, and these can be compared with the expected values of the area in which he was later buriedwhich can show whether or not the individual spent their childhood in the same area.
“Interestingly, the clear presence of at least one non-local female individual after 50 BC post-marital residency models and with dietary changes revealed by the analysis of the stable isotopes of carbon and nitrogen”, comments the biomolecular archaeologist Domingo C. Salazar from the University of Valencia.
“It could very well mean that once a greater degree of human mobility developed in the region, the influence of newcomers contributed to it reduce attendance of the traditional elements of this long-standing culture,” he adds. Experts believe that all of these influences may have led to the demise of shell mound architecture.
“Our results show that the Sambaqui communities on the south and southeast coasts do not represent genetically homogeneous populations. both regions showed different demographic trajectoriesperhaps due to the low mobility of coastal groups,” states the lead author Cosimo Post from the Senckenberg Center for Human Evolution and the Paleoenvironment at the University of Tübingen.
The scientist warns that the observations contrast with the cultural similarities described in the archaeological record. “We need to conduct more regional and micro-scale studies to learn more about South America’s genomic history,” he concludes.
Ferraz T. et al. “Genomic History of Coastal Societies of Eastern South America” Ecology of nature and evolution (2023)