Genomic history of coastal societies from eastern South America

Abstract

Sambaqui (shellmound) societies are among the most intriguing archaeological phenomena in pre-colonial South America, extending from approximately 8,000 to 1,000 years before present (yr bp) across 3,000 km on the Atlantic coast. However, little is known about their connection to early Holocene hunter-gatherers, how this may have contributed to different historical pathways and the processes through which late Holocene ceramists came to rule the coast shortly before European contact. To contribute to our understanding of the population history of indigenous societies on the eastern coast of South America, we produced genome-wide data from 34 ancient individuals as early as 10,000 yr bp from four different regions in Brazil. Early Holocene hunter-gatherers were found to lack shared genetic drift among themselves and with later populations from eastern South America, suggesting that they derived from a common radiation and did not contribute substantially to later coastal groups. Our analyses show genetic heterogeneity among contemporaneous Sambaqui groups from the southeastern and southern Brazilian coast, contrary to the similarity expressed in the archaeological record. The complex history of intercultural contact between inland horticulturists and coastal populations becomes genetically evident during the final horizon of Sambaqui societies, from around 2,200 yr bp, corroborating evidence of cultural change.

Late shellmound occupation in southern Brazil: A multi-proxy study of the Galheta IV archaeological site

“…Determination of biological sex and precise age proved challenging due to poor preservation and/or the absence of diagnostic skeletal elements. The biological sex of two individuals (Burial 3b and 5) were identified as female through DNA analysis [ 25 ]. Additionally, human bone and teeth were retrieved from zooarchaeological samples.…”

“…The second explanation suggests that the progressive abandonment of the traditional sambaqui -building practices was influenced by environmental changes, potentially triggered by climate fluctuations or sea level variations [ 6 , 19 – 24 ]. Alternatively, it is plausible that a combination of environmental and cultural factors contributed to the decrease of these sites in the region [ 18 , 25 ].…”

“…Archaeogenetic analysis of one individual buried at Galheta IV showed greater affinity with sambaquis populations rather than with Jê groups [ 25 ]. However, there is no information available about the geographical provenance of the other individuals buried at the site.…”

“…Archaeogenetic analyses of Amerindian populations [ 25 , 55 ] indicate that human skeletal remains of the sambaqui Jabuticabeira II, located only 20 km from Galheta IV, have a genetic affinity with the present-day Kaingang, who are descendants of the Southern proto - Jê . This genetic data corroborates the idea that these shellmounds societies share a common Jê ancestry and had interbred with those populations in recent times [ 25 ].…”

“…Archaeogenetic analyses of Amerindian populations [ 25 , 55 ] indicate that human skeletal remains of the sambaqui Jabuticabeira II, located only 20 km from Galheta IV, have a genetic affinity with the present-day Kaingang, who are descendants of the Southern proto - Jê . This genetic data corroborates the idea that these shellmounds societies share a common Jê ancestry and had interbred with those populations in recent times [ 25 ]. Our study aims to build upon this genetic evidence by exploring archaeological traces of Jê interaction with the sambaquis at Galheta, seeking to understand the identities of the occupants during this historical period.…”