Since this is a serious article about people eating human brains instead of other wholesome things that under certain circumstances can destroy human brains anyway, here’s the obligitory opening reference to the best horror film on the subject of brain-eating ever made. With that out of the way, let’s talk about kuru. This is a disease that people get when they eat human brains. Among many Stone-Age tribes in New Guinea, eating the brain as a way of honoring the deceased was a common practice at funerals in the absence of Teleflora. The New Guinea kuru epidemic reached its height in the 1960’s; between 1957 and 1968, over 1,100 of the South Fore tribes died from kuru. Eight times more women than men contracted the disease and it affected small children and the elderly at a high rate as well. This is to be expected, since women were the prime participants in mortuary cannibalism rituals there.

The medical cause of kuru was found to be not a germ or virus but instead an unusual brain protein now termed a prion. All proteins in organisms fold into biologically active 3-D shapes; by definition, the biological activity of a prion is to reshape another protein in its own “deformed” image. This leads to a slow chain-reaction that accumulates useless prion proteins in the victim’s brain until severe psychological symptoms and ultimately death occurs. Eat the prions in someone else’s brain, the process continues in your own brain. Kuru was the first well-researched example of these so-called Spongiform Encephalopathy Diseases.

The reason why genes in the human brain would ever evolve to make these newly-discovered prion proteins is an active area of discovery. This week, research was published showing that evolution and natural selection apparently worked to keep it from happening. “Selection for these [anti-prion DNA] polymorphisms has been very widespread or happened very early in the evolution of modern humans, before human beings spread all over the planet,” said researcher John Collinge of University College in London. “We can’t say which of those it is; but the obvious implication is that prion disease has provided the selection pressure.” Collinge’s group found mutations protecting against prion diseases were common, and found with just about the same frequency everywhere. The evidence suggests the genetic mutations date back 500 000 years, leading to the currently disturbing but increasingly widespread belief that Stone Age cannibalism was widespread.