A genomic perspective on South American human history

Abstract

It has generally been accepted that the current indigenous peoples of the Americas are derived from ancestors from northeastern Asia. The latter were believed to have spread into the American continent by the end of the Last Glacial Maximum. In this sense, a joint and in-depth study of the earliest settlement of East Asia and the Americas is required to elucidate these events accurately. The first Americans underwent an adaptation process to the Americas’ vast environmental diversity, mediated by biological and cultural evolution and niche construction, resulting in enormous cultural diversity, a wealth of domesticated species, and extensive landscape modifications. Afterward, in the Late Holocene, the advent of intensive agricultural food production systems, sedentism, and climate change significantly reshaped genetic and cultural diversity across the continent, particularly in the Andes and Amazonia. Furthermore, starting around the end of the 15th century, European colonization resulted in massive extermination of indigenous peoples and extensive admixture. Thus, the present review aims to create a comprehensive picture of the main events involved in the formation of contemporary South American indigenous populations and the dynamics responsible for shaping their genetic diversity by integrating current genetic data with evidence from archeology, linguistics and other disciplines.

Biogeographic Perspectives on Human Genetic Diversification

“…As a consequence of being the last step in the human journey, the Indigenous populations from America present the lowest genetic diversity among continental populations due to the limited time for diversification within the American continent and during the Beringia Standstill ( Reich et al 2012 ; Castro e Silva et al 2022 ). The Beringia Standstill refers to the genetic isolation period of the proto-American population, comprising around 8,000 yr and restricted to a land bridge that connected Asia to America during the last glaciation ( Hoffecker et al 2014 ).…”

“…Different studies focused on Amazonian populations have elucidated how the settlement of this region occurred and the significant genetic diversity found in each area, establishing connections between geography, language, genetics, and culture among South American Indigenous populations ( Arias et al 2018 ; Gnecchi-Ruscone et al 2019 ; Barbieri et al 2019 ; Castro e Silva et al 2020 , 2021 , 2022 ). These studies demonstrated the great mobility of past native populations in South America, known for their present-day strong population structure and prevalence of small groups of individuals.…”

“…The impact of European colonization was devastating across the continent but especially severe on the Atlantic coast of South America, where 99% of the population was wiped out. Another interesting point from recent demographic studies is that in the Amazon region, this population decline began five centuries before European colonization and was worsened by the arrival of Europeans ( Castro e Silva et al 2022 ). The causes of this precontact population collapse are unclear; however, archaeological and paleobotanical data corroborate the genetic data ( Bush et al 2021 ; Schmidt et al 2023 ).…”