The Europeans who arrived in Sydney Cove in Australia from the 1780s onwards weren鈥檛 decimated by disease after contact with the local Aboriginal people, whereas the reverse was all too true. Were the local population free of contagious diseases?
鈥� The local population weren鈥檛 free of contagious diseases. But the diseases would have been fewer and less virulent than those carried by the Europeans.
In small communities, infectious diseases tend to evolve lower virulence. This is because a more virulent disease kills off a big proportion of the population. A small population might then die out altogether, and with no one left to infect, the pathogen dies out too. So survival of the disease-causing organism favours a less virulent form that enables the host population to persist.
Advertisement
The Europeans came from places with large and dense populations and relatively high levels of movement between population centres. These factors favoured increased transmission of virulent diseases, and more of them, aggravated by the poor hygiene standards of the time.
Europeans were also probably exposed to a wider variety of pathogens, so their immune systems may have been better primed than those of the local people to deal with new diseases.
Richard Parkins
Cambridge, UK
鈥� Many pathogens that were common in Europe at that time had jumped from domesticated animals to humans. That may have been the origin of measles, smallpox and tuberculosis, for example. Subsequent mutations enabled human-to-human infection and possibly epidemics.
In Africa and Eurasia, immunity developed to such diseases so there were always survivors. In the New World of the Americas and Oceania, the populations had no immunity to these contagions, so they were decimated, either accidentally or, in some cases, deliberately.
What of the future? Clare Wilson writes that today鈥檚 mass air travel may thwart pandemics by seeding immunity far and wide (10 November 2018, p 10).
David Muir
Edinburgh, UK
鈥� Aboriginal Australians were at a severe disadvantage regarding disease resistance compared with the Europeans who arrived in Sydney Cove. Europeans, living on the western edge of a great land mass, were far from isolated, with much mixing of peoples and animals from far and wide.
鈥淢any pathogens that were common in Europe jumped from domesticated animals to humans鈥�
In contrast, the Aboriginal people had been relatively isolated from this kind of mixing on their island continent for at least 40,000 years. The Europeans arrived in Sydney in January 1788. By April 1789, Aborigines there had been all but wiped out by smallpox.
Terry Dwyer
Willoughby, New South Wales, Australia
We pay 拢25 for every answer published in 快猫短视频. To answer this question 鈥� or ask a new one 鈥� email lastword@newscientist.com.
Questions should be scientific enquiries about everyday phenomena, and both questions and answers should be concise. We reserve the right to edit items for clarity and style. Please include a postal address, daytime telephone number and email address.
快猫短视频 retains total editorial control over the published content and reserves all rights to reuse question and answer material that has been submitted by readers in any medium or in any format.
You can also submit answers by post to: The Last Word, 快猫短视频, 25 Bedford Street, London WC2E 9ES.