A new modeling study uses historical and epidemiological data to argue that the 1789 smallpox epidemic among Indigenous Australians likely began with British medical material brought by the First Fleet, challenging earlier theories of northern introduction
The origins of the catastrophic 1789 smallpox epidemic that devastated Indigenous Australian communities have long been debated. Recent research published in Nature Human Behaviour applies mathematical modeling to historical and demographic data, concluding that the outbreak most likely began with the arrival of the British First Fleet in 1788, rather than through contact with Indonesian islanders in northern Australia.
Tracing the Outbreak
The First Fleet, a convoy of 11 British ships including convict transports and supply vessels, landed at Botany Bay in January 1788 before relocating to Sydney Cove. While no cases of active smallpox were recorded among the fleet's passengers or crew, British medical practice at the time involved carrying vials of dried smallpox scabs for inoculation-a method predating Edward Jenner's vaccine. The study's authors suggest these preserved scabs, which could retain infectious material for months, were the most plausible source of the virus that sparked the epidemic.
Some historians have questioned whether the smallpox virus could survive the eight-month voyage from England. However, the research team notes that the fleet stopped at Cape Town and Rio de Janeiro, where medical supplies could have been replenished, reducing the time infectious material needed to remain viable. The modeling indicates that the pattern and speed of the epidemic's spread in southeastern Australia are consistent with an introduction near the First Fleet's landing site, rather than from the distant tropical north.
Evaluating Competing Theories
Alternative explanations have proposed that smallpox entered Australia via Makassan fishermen from Sulawesi, who had seasonal contact with northern coasts. However, the new study's computer models show that an outbreak beginning in the sparsely populated north could not have reached the southeast in the observed timeframe, given the vast distances and environmental barriers. Instead, the earliest and most severe impacts were recorded near Port Jackson, aligning with the First Fleet's arrival and settlement activities.
The research estimates that the epidemic caused the deaths of approximately 220,000 Indigenous Australians, a figure far exceeding previous official estimates. The authors argue that early 20th-century population counts dramatically underestimated the pre-contact Indigenous population, in part because they were conducted after a century of disease, violence, and displacement had already reduced numbers.
Reassessing Population Impact
In addition to modeling the epidemic's spread, the researchers reference ongoing work suggesting that up to 3 million Indigenous Australians may have lived on the continent at the time of British colonization, with the theoretical carrying capacity reaching as high as 5 million in resource-rich regions. These revised estimates are based on archaeological evidence from early Indigenous settlements and environmental modeling, challenging the long-standing figure of 300,000 derived from much later, post-epidemic observations.
Independent historians reviewing the study agree that the evidence strongly favors a southeastern origin for the outbreak, closely linked to the First Fleet's arrival and the use of preserved smallpox material for inoculation. The research also highlights the limitations of historical documentation and the need for interdisciplinary approaches combining archaeology, epidemiology, and Indigenous oral histories to reconstruct the true scale and impact of colonial-era epidemics.
Limits of the Evidence
While the modeling provides a plausible scenario for the introduction and spread of smallpox, direct archaeological evidence-such as physical remains of the inoculation material or contemporaneous Indigenous burials with diagnostic lesions-is lacking. The study relies on historical records, demographic modeling, and the known practices of British medical personnel. The absence of recorded smallpox cases among the fleet's members does not rule out the possibility of accidental transmission, especially given the limited understanding of disease mechanisms at the time.
The findings underscore the profound demographic and cultural consequences of the epidemic, which contributed to the rapid disruption of Indigenous societies in southeastern Australia. They also illustrate the challenges of reconstructing population histories in contexts where written records are incomplete and archaeological evidence is fragmentary or absent.
Understanding the spread of infectious diseases in the past often depends on indirect evidence, such as historical accounts, demographic modeling, and the archaeological context of settlements and burials. Mathematical models can help test competing scenarios by simulating how a disease might move through a landscape given known population densities, travel routes, and environmental barriers. However, these models are only as reliable as the underlying data and assumptions. In the case of the 1789 smallpox epidemic, the lack of direct skeletal or molecular evidence means that conclusions must remain provisional, pending new discoveries or advances in analytical techniques.
