A paper dedicated to microbes that causes infectious diseases.
Scholars examined large number of ancient human remains for the purpose to detect ancient microbes. They came to the conclusion that the shift to farming and especially to pastoralism increased the number of infectious diseases. The cohabitation with livestock is the main cause of this increase. In Europe the mass migration from steppe at 3000BC coincide with the peak of microbe DNA detected in ancient remains. They suppose that steppe pastoralists who heavily relied on livestock acquire more immunity than those farmers in Europe relying mostly on crop raising. Which can explain the population change in Europe. Here an excerpt from their conclusion.
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We observed some of the highest detection rates at roughly 5,000 bp, a time of substantial demographic changes in Europe due to the migration of Steppe pastoralists and the displacement of earlier populations4,5. Steppe pastoralists, through their long-term continuous exposure to animals, probably developed some immunity to certain zoonoses and their dispersals may have carried these diseases westwards and eastwards. Consequently, the genetic upheaval in Europe could have been facilitated by epidemic waves of zoonotic diseases causing population declines, with depopulated areas subsequently being repopulated by opportunistic settlers who intermixed with the remaining original population. This scenario would mirror the population decline of Indigenous people in the Americas following their exposure to diseases introduced by European colonists55,56. Our findings support the interpretation of increased pathogen pressure as a likely driver of positive selection on immune genes associated with the risk of multiple sclerosis in Steppe populations roughly 5,000 years ago57, and immune gene adaptations having occurred predominantly after the onset of the Bronze Age in Europe9
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