New Scientist reports on a new study on how a gene that gives protection against the deadly brain disease kuru became more common in people exposed to the condition through their cannibalistic tradition of eating the bodies of dead relatives.
Kuru is a prion disease, meaning the damage is caused by a poorly arranged or folded protein molecule which can trigger the same damaging changes in other proteins it comes into contact with.
The condition is related to what we know as ‘mad cow disease’ and causes a distinctive form of shaking, brain degeneration and eventually leads to death. It was restricted to the South Fore people of Papua New Guinea who seemed to pass on the condition by their tradition of to eating deceased relatives at mortuary feasts.
This new study shows that over time a new variant of the PRNP gene emerged in the population which gave protection against kuru.
Because kuru is deadly and was widespread, the emergence of the gene shows evolution in action:
The mutation first arose about 200 years ago by accident in a single individual, who then passed it down to his or her descendants. “When the kuru epidemic peaked about 100 years back, there were maybe a couple of families who found that they and their children survived while all their neighbours were dying, and so on to today’s generation, who still carry the gene,” says Mead. “So it was a very sudden genetic change under intense selection pressure from the disease,” he says.
If you want some background on kuru and how prion diseases affect the brain, you can’t go far wrong with a fantastic Neurophilosophy article from last year.