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Post-invasion demography of prehistoric humans in South America


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 prehistory1,2,3,4,5,6,7. Yet remarkably little is known about human population dynamics during colonization, subsequent expansions, and domestication2,3,4,5. 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 animals4,8 had a minimal impact on population carrying capacity. Only with widespread sedentism, beginning ~5 ka4,8, did a second demographic phase begin, with evidence for exponential population growth in cultural hotspots, characteristic of the Neolithic transition worldwide9. The unique extent of humanity’s ability to modify its environment to markedly increase carrying capacity in South America is therefore an unexpectedly recent phenomenon.

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Figure 1: Archaeological sites in database.
Figure 2: Kernel density maps of occupied area.
Figure 3: Climatic and radiocarbon records for 14 ka to 2 ka.
Figure 4: A two-phase model for the human invasion of South America.

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We thank A. Barnosky, J. Kang, N. Rosenberg, E. Lindsey, N. Villavicencio, L. Frishkoff, K. Solari, J. Hsu, and H. Frank for conversations and feedback on the paper, as well as E. Jewett and M. Edge for discussions of statistical methods. We also greatly appreciate assistance from the Stanford Geospatial Center. This work was stimulated by discussions of an NSF-funded group (EAR 1148181) comparing the timing of megafaunal extinctions with archeological and palaeoenvironmental data in South America. We acknowledge support from NSF grant BCS 1515127, as well as NSF Graduate Research and ARCS fellowships to A.G., a Stanford Interdisciplinary Graduate Fellowship to A.M.M, and a Gabilan Fellowship to E.A.H. Radiocarbon data and associated information are available in the Supplementary Information.

Author information

Authors and Affiliations



A.G. conducted analyses and wrote the first draft of the paper. A.M.M. collected and collated the database, and conducted ArcGIS analyses. E.A.H. advised the analyses and initiated the project. All authors interpreted results, and contributed to framing and editing of the paper.

Corresponding author

Correspondence to Amy Goldberg.

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The authors declare no competing financial interests.

Extended data figures and tables

Extended Data Figure 1 Kernel Density estimates of occupied area for alternative time bins.

Estimates of occupied area in 1,000-year time bins for dates not present in Fig. 2, considering uniquely occupied sites in each time bin.

Extended Data Figure 2 Kernel Density estimates of occupied area for fixed search radius.

Estimates of occupied area in 1,000-year time bins for dates present in Fig. 2, using a fixed radius for all time slices of 660 km.

Extended Data Figure 3 Statistical evaluation of constant population size in the mid-Holocene.

The simulated 98% confidence interval (grey) for radiocarbon density under a constant population size in 5-year bins, with the observed SCPD for the data (black).

Extended Data Figure 4 Observed oscillations are outside the variation of simulated constant size.

A histogram of the variance of 200 simulated constant size SCPDs, with the observed variance of density in the observed SCPD from 9 to 5.5 ka outside the distribution of those simulated.

Extended Data Figure 5 Inferred population size over time.

Assuming colonization of South America 14.8 ka by a population of size N0, we plot the relative increase in population size over time under the two-phase model (black). Carrying capacity (grey) occurs approximately 8.5 ka with a relative population size N/N0 = 274.6, and a final population size at 2 ka of N/N0 = 616.6.

Extended Data Figure 6 SCPD for Andean/Pacific Coastal Region.

The Pacific Coast region and Andes, which represents 52% of dates and multiple of the major cultural centres, show a similar trend as the SCPD for the continent.

Extended Data Table 1 Model likelihoods and model choice

Supplementary information

Supplementary Data

This file contains Supplementary Dataset 1. (XLSX 471 kb)

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Goldberg, A., Mychajliw, A. & Hadly, E. Post-invasion demography of prehistoric humans in South America. Nature 532, 232–235 (2016).

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