Australia Was Home to Over Two Million Indigenous People Before Colonisation, Study Finds

The scale of Australia’s Indigenous population before European colonisation has been debated for more than a century, and the answers have always been contested. Now a major interdisciplinary study published in Nature Human Behaviour offers the most rigorous estimate to date, concluding that roughly 2.22 million Aboriginal and Torres Strait Islander people lived on the continent at the time of colonial invasion in 1788. That figure, corresponding to a population density of about 0.29 people per square kilometre, is dramatically higher than many historical accounts have suggested, and it forces a sobering recalculation of what the decades after 1788 actually meant in human terms.

The research team, led by Alan N. Williams of the University of New South Wales and Corey J. A. Bradshaw of Flinders University, brought together an unusually broad set of evidence streams. Rather than relying on any single line of inquiry, the authors compiled ethnographic observations recorded by explorers and colonial officials, archaeological reconstructions based on radiocarbon dates from thousands of occupation sites, and genetic estimates of effective population size drawn from ancient and contemporary Aboriginal mitogenomes and genomes. Each stream carries its own biases, but the strength of the study lies in where the independent lines of evidence converge.

Technically, the team modelled the continent’s human carrying capacity using climate and net primary productivity data. They drew on high-resolution palaeoclimate reconstructions, including statistics-based global terrestrial climate products covering the late Quaternary, and combined these with vegetation productivity estimates to predict how many hunter-gatherers Australia’s environments could plausibly support. These capacity models were calibrated against a global hunter-gatherer population density dataset, which constrains expected densities using factors such as seasonality, diet composition, productivity and pathogen load. The result was a spatially explicit map of plausible pre-colonial densities across the continent, from resource-rich coastal strips to the arid interior.

Crucially, the authors found that the modelled carrying-capacity estimates and the genetics-based reconstructions agreed closely with one another, while historical and ethnographic accounts tended to fall below them. Historical estimates were shaped by observers who saw a continent already disrupted by disease and displacement, and who systematically undercounted populations in regions they never visited. By contrast, the bootstrapped median of 2.22 million people emerged from the congruence of ecological modelling and genetic demography, with confidence intervals built by resampling the underlying estimates ten thousand times. The agreement between such independent methods is what gives the new figure its persuasive force.

The implications of a pre-colonial population of this size are profound. The researchers used a stochastic demographic model to work backwards from the earliest reliable census records, which recorded only around 92,000 to 134,000 Indigenous people by the beginning of the twentieth century. For the population to fall from a median of 2.22 million to those census levels, approximately 28,200 excess deaths per year would have had to occur through the late eighteenth and early nineteenth centuries, amounting to roughly 2.06 million excess deaths in total attributable to the consequences of colonial invasion.

Those excess deaths were driven by a combination of documented forces. Lethal introduced diseases, including at least three major smallpox outbreaks, swept through communities with no acquired immunity, and the study cites companion stochastic modelling indicating rapid smallpox spread and mass mortality following colonial exposure. Measles, influenza, tuberculosis and leprosy added further burdens. But disease alone does not explain the demographic collapse. Frontier violence, recorded in the Colonial Frontier Massacres database covering 1788 to 1930, and the structural violence of dispossession, forced removal and the deliberate destruction of food and water resources compounded the mortality. The paper is explicit that these findings are confronting, and it frames the work explicitly as an exercise in truth-telling.

The demographic modelling also identifies a symbolic and ecological nadir. According to the study’s trajectory, the non-Indigenous population first exceeded the Indigenous population around 1847, which was also the year the continent’s total population reached its lowest point since before the invasion, at roughly 1.07 million people. The authors note this may represent the smallest human population on the Australian landmass in more than fifty thousand years, a startling reversal given that Aboriginal people had sustainably occupied and managed the continent since arriving in Sahul tens of millennia ago, developing sophisticated fire management and ecosystem engineering practices that shaped the landscape itself.

What distinguishes this work from earlier attempts, such as the classic twentieth-century estimates by Radcliffe-Brown and Birdsell, is its transparency and reproducibility. All data and R code are openly available through Zenodo, allowing other researchers to interrogate the assumptions, rerun the bootstrapping procedures and test alternative demographic scenarios. The sensitivity analyses show how the estimated excess deaths vary across the plausible range of initial population sizes, from one million to five million, giving readers a clear picture of where the central estimate sits within the uncertainty envelope rather than presenting a single deceptively precise number.

The study was conducted with substantial Indigenous participation and oversight, approved by the Flinders University Human Research Ethics Committee, and authored by researchers including First Nations scholars from the Gujaga Foundation and institutions across the country. The team acknowledges the Traditional Owners of the lands where they work and frames the research within reconciliation efforts. Importantly, the paper does not end with the collapse. Recent census data show that the Indigenous population of Australia has recovered strongly, surpassing 800,000 people by 2021, a trajectory of survival and renewal that the authors present as the essential counterpoint to the mortality estimates.

For demographers, archaeologists and historians, the study provides a new quantitative baseline for understanding pre-colonial Australia as a densely occupied, intensively managed continent rather than an empty wilderness awaiting settlement. For the broader public, the number 2.22 million reframes the colonial period: a society of millions was reduced to a fraction of itself within a few generations. The authors hope that rigorous, evidence-based quantification of this demographic catastrophe can contribute to national truth-telling processes, giving the scale of loss a firm empirical footing while documenting the resilience of the descendants of those who survived.

Subject of Research: Estimating the pre-colonial population size of Indigenous Australians and the demographic impact of European colonial invasion

Article Title: Large estimated size of the Australian Indigenous population before its extensive decline following colonial invasion

Article References: Williams, A. N., Tobler, R., Griffiths, B., Ulm, S., Nitschke, M. C., Bird, M. I., Ingrey, S., Saltré, F., Beller, K., McNiven, I. J., Pitt, N., Russell, L., Paterson, A., Wilson, C., & Bradshaw, C. J. A. (2026). Large estimated size of the Australian Indigenous population before its extensive decline following colonial invasion. Nature Human Behaviour. https://doi.org/10.1038/s41562-026-02571-9

Image Credits: AI Generated

DOI: 10.1038/s41562-026-02571-9

Keywords: Indigenous Australians, pre-colonial population, colonial invasion, demography, carrying capacity, excess deaths, archaeology, population genetics, frontier violence, smallpox, truth-telling, Nature Human Behaviour