Minimum founding populations for the first peopling of Sahul

Abstract

The timing, context and nature of the first people to enter Sahul is still poorly understood owing to a fragmented archaeological record. However, quantifying the plausible demographic context of this founding population is essential to determine how and why the initial peopling of Sahul occurred. We developed a stochastic, age-structured model using demographic rates from hunter-gatherer societies, and relative carrying capacity hindcasted with LOVECLIM’s net primary productivity for northern Sahul. We projected these populations to determine the resilience and minimum sizes required to avoid extinction. A census founding population of between 1,300 and 1,550 individuals was necessary to maintain a quasi-extinction threshold of 0.1. This minimum founding population could have arrived at a single point in time, or through multiple voyages of ≥130 people over ~700–900 years. This result shows that substantial population amalgamation in Sunda and Wallacea in Marine Isotope Stages 3–4 provided the conditions for the successful, large-scale and probably planned peopling of Sahul.

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Fig. 1: Estimating quasi-extinction probability for the first Sahul population.
Fig. 2: Change in net primary production and indicative human carrying capacity.

Data availability

All data are available for download at github.com/cjabradshaw/SahulHuman.

Code availability

All R code is available for download at github.com/cjabradshaw/SahulHuman.

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Acknowledgements

This study was supported by the Australian Research Council through a Centre of Excellence grant (CE170100015) to R.G.R., S.U., M.I.B., Z.J., C.J.A.B. and L.S.W., fellowships to S.U. (FT120100656), M.I.B. (FL140100044), R.G.R. (FL130100116), Z.J. (FT150100138) and L.S.W. (FT180100407), and an Australian Government Research Training Program Award to K.N.

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C.J.A.B. and F.S. designed the research. C.J.A.B. performed the analysis and sourced the data. C.J.A.B., F.S., S.U., A.N.W. and M.I.B. wrote the paper. All other co-authors contributed substantially to developing the manuscript.

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Correspondence to Corey J. A. Bradshaw.

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Bradshaw, C.J.A., Ulm, S., Williams, A.N. et al. Minimum founding populations for the first peopling of Sahul. Nat Ecol Evol 3, 1057–1063 (2019). https://doi.org/10.1038/s41559-019-0902-6

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