Post by Admin on Dec 24, 2023 20:47:58 GMT
Discussion
The oldest individual newly sequenced in this study, Capelinha_10400BP, does not carry a distinct genetic similarity to any other early Holocene or younger populations but shows a generalized affinity to ancient Brazilian and present-day South American groups. This suggests that his source population had a basal placement among the initial radiation event into South America. Moreover, both Capelinha_10400BP and Sumidouro_10100BP lack a significant affinity to Anzick-1-related ancestry (Supplementary Data 4 and Extended Data Fig. 4). These individuals predate by more than a thousand years the earliest occurrence of South American individuals without evidence of this ancestry (Cuncaicha_9000BP and Lauricocha_8600BP), challenging the scenario of two subsequent waves of expansion into South America, the first one with and the second one without Anzick-1-related ancestry63. However, we caution that this result could be affected by the lack of statistical power, and another potential scenario would involve early South American settlers carrying different proportions of this genetic component. Additional genomes from other regions of South America would be necessary to assess whether populations carrying Anzick-1-related ancestry were replaced by or intermixed with other early Holocene groups.
The genetic distinctiveness between early Holocene individuals from the Lagoa region, Capelinha_10400BP and Loca Do Suin_9100BP, also indicates greater genetic variation among early Brazilian hunter-gatherers than previously expected. Within the Lagoa region, early Holocene individuals mostly derived from a common ancestral group, as shown by the high genetic affinity between the Sumidouro_10100BP and Lapa do Santo_9600BP groups. We also detected two distinct genetic attractions between Lapa do Santo_9600BP and late Holocene groups. The first signal was observed with the southern Sambaqui JabuticabeiraII_~2400BP group and Cabeçuda_3200BP, and the second with the Amazonian individual Palmeiras Xingu_500BP (Extended Data Fig. 3a). The genetic connection between individuals separated by thousands of kilometres and thousands of years might indicate the survival of this ancestry through time (Extended Data Fig. 8).
The Population Y signal related to Andamanese and Australasian populations could not be detected in the early Holocene Capelinha_10400BP individual or in the Amazonian Palmeiras Xingu_500BP individual. However, we report this signal in individuals from the southern sambaqui sites of Cabeçuda_3200BP and JabuticabeiraII_~2400BP. The latter is the only pre-colonial group exhibiting higher affinity to non-American ancestries even in direct comparison to another ancient Brazilian group (Supplementary Data 7). If confirmed, the sporadic identification of the Population Y signal in ancient individuals with different ancestries, locations and time periods across Brazil—where this signal was first described—suggests a higher probability that it derives from genetic structure in the founding Native American population65,77 than from multiple independent migrations into the Americas62,82.
Middle Holocene riverine Sambaqui individuals (Laranjal_6700BP and Moraes_5800BP) are strongly related, confirming a local genetic structure63, which might correspond to a distinct genetic group when compared with coastal Sambaqui populations. Individuals from Laranjal and Moraes also show a higher affinity with south coast than with southeast coast Sambaqui groups, suggesting potential genetic links between geographically closer populations. However, the two sites represent only a small portion of the riverine sambaquis, and additional individuals should be genetically analysed to confirm this pattern.
The coastal Sambaqui groups Cabeçuda_3200BP and JabuticabeiraII_~2400BP showed high genetic affinity with each other (Fig. 2 and Supplementary Data 2). Both sites, only 20 km apart, exhibit genetic similarities to contemporaneous individuals from Cubatão I, about 200 km further north. The late burials from Jabuticabeira II (~2,200 yr BP and ~1,300 yr BP) display an incremental genetic attraction to southern Jê ancestry represented by both recent and present-day Kaingang (Figs. 2b and 3a, Extended Data Fig. 5 and Supplementary Data 5). JabuticabeiraII_102_1300BP has an 87Sr/86Sr isotope ratio above the range observed for older individuals at Jabuticabeira II (Extended Data Fig. 9) and could thus be a non-local individual who spent earlier years in continental areas (that is, the Catarina highlands) or in a different location on the coast45. The presence of a non-local individual after 2,000 yr BP coincides with changes in the post-marital residence patterns47 and with dietary changes revealed by isotopic analyses44,83. The strong genetic affinity between Kaingang and JabuticabeiraII_102_1300BP demonstrates a genetic relationship between proto-Jê groups from the southern Brazilian highlands and post-2,000 yr BP coastal groups. However, this evidence precedes the arrival of Taquara-Itararé ceramics on the coast by around a hundred years39. Considering that Kaingang ancestry is already detected in Sambaqui individuals before the 2,000 yr BP horizon of cultural change, as indicated by JabuticabeiraII_111/112_~2200BP, our results show that the intensification of contacts between inland and coastal populations was concomitant with a sharp decline in shellmound construction39 and shortly before the appearance of fishmounds. This indicates that cultural contacts associated with genetic interactions at a time of unprecedented environmental and ecological changes may have influenced the end of shellmound architecture. Our results also show that one individual from Galheta IV (Galheta IV_1200BP), a fishmound with Taquara-Itararé ceramics, is genetically similar to the JabuticabeiraII_~2400BP group and Cabeçuda_3200BP. This suggests some level of demic continuity after the arrival of ceramics in the region (Fig. 2 and Supplementary Data 2 and 5).
On the southeast coast, the sambaqui do Limão individuals carry at least two distinct genetic ancestries. The Limão_2700BP individual and the Limão_~1900BP group show a significant affinity to the northeastern hunter-gatherer from Pedra do Alexandre2_undated and to the Amazonian individual Palmeiras Xingu_500BP. Despite cultural similarities, we do not observe an extra genetic affinity between individuals from the sambaqui do Limão and sambaqui sites on the southern coast (Fig. 2 and Extended Data Fig. 3c). The genetic link between the older sambaqui do Limão individuals and hunter-gatherers from northeast Brazil as well as present-day Xávante from central Brazil may explain their separation from contemporaneous groups on the southern coast. Furthermore, the high affinity of Limão_500BP with Tupi-speaking Zoro provides the first ancient genomic evidence for the spread of Tupi-related ancestry to the Brazilian southeast coast. The Tupi-Guarani expansion from southeastern Amazonia across the Atlantic coast of Brazil is a well-known demographic phenomenon38,42,53,54,55,56,57, and our results reveal an arrival of Tupi-related ancestry on the coast of Espírito Santo by at least 500 yr BP (Supplementary Data 6).
In conclusion, our results demonstrate that Sambaqui societies from the south and southeast coasts were not a genetically homogenous population. Both regions had different demographic trajectories, possibly due to the low mobility of coastal groups2,21,29. This contrasts with the cultural similarities described in the archaeological record and highlights the need to perform more regional and micro-scale studies to improve our understanding of the genomic history of eastern South America.
The oldest individual newly sequenced in this study, Capelinha_10400BP, does not carry a distinct genetic similarity to any other early Holocene or younger populations but shows a generalized affinity to ancient Brazilian and present-day South American groups. This suggests that his source population had a basal placement among the initial radiation event into South America. Moreover, both Capelinha_10400BP and Sumidouro_10100BP lack a significant affinity to Anzick-1-related ancestry (Supplementary Data 4 and Extended Data Fig. 4). These individuals predate by more than a thousand years the earliest occurrence of South American individuals without evidence of this ancestry (Cuncaicha_9000BP and Lauricocha_8600BP), challenging the scenario of two subsequent waves of expansion into South America, the first one with and the second one without Anzick-1-related ancestry63. However, we caution that this result could be affected by the lack of statistical power, and another potential scenario would involve early South American settlers carrying different proportions of this genetic component. Additional genomes from other regions of South America would be necessary to assess whether populations carrying Anzick-1-related ancestry were replaced by or intermixed with other early Holocene groups.
The genetic distinctiveness between early Holocene individuals from the Lagoa region, Capelinha_10400BP and Loca Do Suin_9100BP, also indicates greater genetic variation among early Brazilian hunter-gatherers than previously expected. Within the Lagoa region, early Holocene individuals mostly derived from a common ancestral group, as shown by the high genetic affinity between the Sumidouro_10100BP and Lapa do Santo_9600BP groups. We also detected two distinct genetic attractions between Lapa do Santo_9600BP and late Holocene groups. The first signal was observed with the southern Sambaqui JabuticabeiraII_~2400BP group and Cabeçuda_3200BP, and the second with the Amazonian individual Palmeiras Xingu_500BP (Extended Data Fig. 3a). The genetic connection between individuals separated by thousands of kilometres and thousands of years might indicate the survival of this ancestry through time (Extended Data Fig. 8).
The Population Y signal related to Andamanese and Australasian populations could not be detected in the early Holocene Capelinha_10400BP individual or in the Amazonian Palmeiras Xingu_500BP individual. However, we report this signal in individuals from the southern sambaqui sites of Cabeçuda_3200BP and JabuticabeiraII_~2400BP. The latter is the only pre-colonial group exhibiting higher affinity to non-American ancestries even in direct comparison to another ancient Brazilian group (Supplementary Data 7). If confirmed, the sporadic identification of the Population Y signal in ancient individuals with different ancestries, locations and time periods across Brazil—where this signal was first described—suggests a higher probability that it derives from genetic structure in the founding Native American population65,77 than from multiple independent migrations into the Americas62,82.
Middle Holocene riverine Sambaqui individuals (Laranjal_6700BP and Moraes_5800BP) are strongly related, confirming a local genetic structure63, which might correspond to a distinct genetic group when compared with coastal Sambaqui populations. Individuals from Laranjal and Moraes also show a higher affinity with south coast than with southeast coast Sambaqui groups, suggesting potential genetic links between geographically closer populations. However, the two sites represent only a small portion of the riverine sambaquis, and additional individuals should be genetically analysed to confirm this pattern.
The coastal Sambaqui groups Cabeçuda_3200BP and JabuticabeiraII_~2400BP showed high genetic affinity with each other (Fig. 2 and Supplementary Data 2). Both sites, only 20 km apart, exhibit genetic similarities to contemporaneous individuals from Cubatão I, about 200 km further north. The late burials from Jabuticabeira II (~2,200 yr BP and ~1,300 yr BP) display an incremental genetic attraction to southern Jê ancestry represented by both recent and present-day Kaingang (Figs. 2b and 3a, Extended Data Fig. 5 and Supplementary Data 5). JabuticabeiraII_102_1300BP has an 87Sr/86Sr isotope ratio above the range observed for older individuals at Jabuticabeira II (Extended Data Fig. 9) and could thus be a non-local individual who spent earlier years in continental areas (that is, the Catarina highlands) or in a different location on the coast45. The presence of a non-local individual after 2,000 yr BP coincides with changes in the post-marital residence patterns47 and with dietary changes revealed by isotopic analyses44,83. The strong genetic affinity between Kaingang and JabuticabeiraII_102_1300BP demonstrates a genetic relationship between proto-Jê groups from the southern Brazilian highlands and post-2,000 yr BP coastal groups. However, this evidence precedes the arrival of Taquara-Itararé ceramics on the coast by around a hundred years39. Considering that Kaingang ancestry is already detected in Sambaqui individuals before the 2,000 yr BP horizon of cultural change, as indicated by JabuticabeiraII_111/112_~2200BP, our results show that the intensification of contacts between inland and coastal populations was concomitant with a sharp decline in shellmound construction39 and shortly before the appearance of fishmounds. This indicates that cultural contacts associated with genetic interactions at a time of unprecedented environmental and ecological changes may have influenced the end of shellmound architecture. Our results also show that one individual from Galheta IV (Galheta IV_1200BP), a fishmound with Taquara-Itararé ceramics, is genetically similar to the JabuticabeiraII_~2400BP group and Cabeçuda_3200BP. This suggests some level of demic continuity after the arrival of ceramics in the region (Fig. 2 and Supplementary Data 2 and 5).
On the southeast coast, the sambaqui do Limão individuals carry at least two distinct genetic ancestries. The Limão_2700BP individual and the Limão_~1900BP group show a significant affinity to the northeastern hunter-gatherer from Pedra do Alexandre2_undated and to the Amazonian individual Palmeiras Xingu_500BP. Despite cultural similarities, we do not observe an extra genetic affinity between individuals from the sambaqui do Limão and sambaqui sites on the southern coast (Fig. 2 and Extended Data Fig. 3c). The genetic link between the older sambaqui do Limão individuals and hunter-gatherers from northeast Brazil as well as present-day Xávante from central Brazil may explain their separation from contemporaneous groups on the southern coast. Furthermore, the high affinity of Limão_500BP with Tupi-speaking Zoro provides the first ancient genomic evidence for the spread of Tupi-related ancestry to the Brazilian southeast coast. The Tupi-Guarani expansion from southeastern Amazonia across the Atlantic coast of Brazil is a well-known demographic phenomenon38,42,53,54,55,56,57, and our results reveal an arrival of Tupi-related ancestry on the coast of Espírito Santo by at least 500 yr BP (Supplementary Data 6).
In conclusion, our results demonstrate that Sambaqui societies from the south and southeast coasts were not a genetically homogenous population. Both regions had different demographic trajectories, possibly due to the low mobility of coastal groups2,21,29. This contrasts with the cultural similarities described in the archaeological record and highlights the need to perform more regional and micro-scale studies to improve our understanding of the genomic history of eastern South America.