Post-invasion demography of prehistoric humans in South America

South America was the last habitable continent to be colonized by humans; using a database of 1,147 archaeological sites and 5,464 radiocarbon dates spanning 14,000 to 2,000 years ago reveals two phases of the population history of the continent—a rapid expansion through the continent at low population sizes for over 8,000 years and then a second phase of sedentary lifestyle and exponential population growth starting around 5,000 years ago. The peopling of South America Amy Goldberg et al . reconstruct the population history of South America, the last habitable continent to be colonized by humans, using a database of 1,147 archaeological sites and 5,465 calibrated radiocarbon dates spanning 14,000 to 2,000 years ago. Rather than the steady spread of people through the continent that might be expected, the data reveal that the continent was populated in two phases. First, humans spread rapidly throughout the continent, but the population remained low for 8,000 years. The second phase began only when sedentary life and farming became widespread, about 5,000 years ago. As the last habitable continent colonized by humans, the site of multiple domestication hotspots, and the location of the largest Pleistocene megafaunal extinction, South America is central to human prehistory 1 , 2 , 3 , 4 , 5 , 6 , 7 . Yet remarkably little is known about human population dynamics during colonization, subsequent expansions, and domestication 2 , 3 , 4 , 5 . Here we reconstruct the spatiotemporal patterns of human population growth in South America using a newly aggregated database of 1,147 archaeological sites and 5,464 calibrated radiocarbon dates spanning fourteen thousand to two thousand years ago (ka). We demonstrate that, rather than a steady exponential expansion, the demographic history of South Americans is characterized by two distinct phases. First, humans spread rapidly throughout the continent, but remained at low population sizes for 8,000 years, including a 4,000-year period of ‘boom-and-bust’ oscillations with no net growth. Supplementation of hunting with domesticated crops and animals 4 , 8 had a minimal impact on population carrying capacity. Only with widespread sedentism, beginning ~5 ka 4 , 8 , did a second demographic phase begin, with evidence for exponential population growth in cultural hotspots, characteristic of the Neolithic transition worldwide 9 . The unique extent of humanity’s ability to modify its environment to markedly increase carrying capa