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A cannibalistic ritual in which the brains of dead tribespeople were eaten by their relatives has triggered one of the most striking examples of rapid human evolution on record, scientists have discovered. In the middle of the 20th century the Fore tribe of the Eastern Highlands province of Papua New Guinea was devastated by a CJD-like disease called kuru, which was passed on by mortuary feasts in which the brains of the dead were consumed.
Although the practice was banned in the 1950s and kuru has disappeared, it has left an imprint on the tribe’s DNA. Research has now identified a genetic mutation unique to the Fore that protects against the brain disease and which has spread swiftly through the population by natural selection.
As the mutation confers high or almost complete resistance to kuru, carriers have a survival advantage and have had more descendants. About 8 per cent of people from the Purosa Valley region, where kuru hit hardest, now have the gene, which is unknown anywhere else in the world.
The findings, from a team led by Simon Mead, of the Medical Research Council Prion Unit at University College London, show how quickly human evolution can respond to new environmental pressures. They are described today in The New England Journal of Medicine as scientists prepare to celebrate the 150th anniversary of the publication of Charles Darwin’s On the Origin of Species on Tuesday.
Professor John Collinge, the director of the prion unit, said: “It’s absolutely fascinating to see Darwinian principles at work here. This community of people have developed their own biologically unique response to a truly terrible epidemic. The fact that this genetic evolution has happened in a matter of decades is remarkable.”
Oral histories provided by elderly members of the Fore tribe suggest that kuru emerged in the early 20th century and developed into a serious epidemic with an annual mortality rate of more than 2 per cent in some villages. It mainly affected women and children, who would eat the remains of dead relatives. Kuru disappeared when cannibal rituals were stopped in the 1950s under the influence of missionaries.