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| Author(s): |
Marcos Araújo Castro e Silva
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Instituto de Biociências (IBIOC/SB) |
| Defense date: | 2021-09-27 |
| Examining board members: |
Tábita Hünemeier;
Eduardo Goes Neves;
Virginia Ramallo;
Andre Menezes Strauss
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| Advisor: | Tábita Hünemeier |
| Abstract | |
The origin of the native americans traces back to northeastern asian peoples which would have reached Beringia during the Last Glacial Maximum and after its end they would have crossed the northern North America ice sheets initiating the settlement of the continent. Excepting the arctic populations, the remaining native americans were formed by a common ancestral population, however some present-day indigenous communities and one ancient individual from Brazil exhibit an additional ancestry component, which presents higher genetic affinity with populations from southern Asia, Melanesia and Australia and has been modelled as a contribution from an unsampled population (Population Y). During the initial settlement which the first americans underwent a process of adaptation to the vast environmental diversity of the Americas, mediated by both biological and cultural evolution, as well as by niche construction, resulting in one of the greatest cultural diversities of the world, with approximately 350 ethnic groups and over 180 native languages in the Amazon alone. Later, during the mid and late Holocene some factors such as the intensification of food production and climate change produced population dynamics that significantly reconfigured the genetic landscape, among these events the Tupí Expansion is probably the most relevant for eastern South America. Furthermore, the European invasion and colonization, starting in the end of the 15th century, led to a massive extermination of the indigenous people, particularly on the Brazilian coast, which was predominantly occupied by the Tupi. Here we analyze unpublished genomic data from 139 contemporary Native Americans from 9 ethnic groups of Brazil, genotyped on the Axiom Human Origins - Affymetrix (49) and Axiom InCor BB - Affymetrix (95) platforms (5 individuals present in both) and merged to public databases of contemporary indigenous communities and ancient individuals. In Chapter 1, we demonstrate that the Australasian genetic affinity signal has high intra- and interpopulation variation, and is much more widely distributed in South America than previously demonstrated, being present further south in the Brazilian midwest region in the Guaraní Kaiowá and also across the Andes in the Chotuna of the northern peruvian coast. Additionally, the population history models corroborate that the initial settlement of the Americas occurred along the Pacific coast route. Whereas, in Chapter 2 we find a pattern of genetic structure partially related to linguistic diversity among the indigenous peoples of eastern and western South America, with at least 3 primary divisions in each region and a transitional group in the western Amazon, including populations from the Andean eastern slopes. However, both genetic variation and homozygosity level are correlated with longitude, in addition to genetic distance, which is correlated with geographic distance, thus suggesting a joint effect of isolation by distance and serial population bottlenecks, possibly dating back to the initial dispersion from Pacific coast. Interestingly, the genetic substructure of contemporary indigenous populations recapitulates the subcontinental ancestry of ancient individuals. We also find evidence of demic expansions in the late Holocene and a greater resistance to post-contact population collapse among western South American groups. Finally, several lines of evidence indicate that the Kokama of the western Amazon underwent a process of linguistic substitution. While in Chapter 3 we show that the Tupiniquim from Espírito Santo, on the Brazilian coast, are descendants of the ancient coastal Tupi branch, furthermore we also date the periods of admixture intensification with European and African peoples, which trace back to some historical events particularly relevant to Brazilian demography. Finally, models based on alternative Tupí expansion hypotheses corroborate the interpretation of the Brazilian archaeologist José P. Brochado, according to which the coastal Tupí (i.e. Tupinambá) and the Guaraní would have diverged and expanded from the Amazon by independent routes, the first following the Amazon River course towards the east and then through the Atlantic coast and the latter going directly south along the rivers to the Paraná Basin. (AU) | |
| FAPESP's process: | 18/01371-6 - Diversity and evolution of Brazilian populations |
| Grantee: | Marcos Araújo Castro e Silva |
| Support Opportunities: | Scholarships in Brazil - Doctorate |