Kuru is an acquired prion disease largely restricted to the Fore linguistic group of the Papua New Guinea Highlands, which was transmitted during endocannibalistic feasts. Heterozygosity for a common polymorphism in the human prion protein gene (PRNP) confers relative resistance to prion diseases. Elderly survivors of the kuru epidemic, who had multiple exposures at mortuary feasts, are, in marked contrast to younger unexposed Fore, predominantly PRNP 129 heterozygotes. Kuru imposed strong balancing selection on the Fore, essentially eliminating PRNP 129 homozygotes. Worldwide PRNP haplotype diversity and coding allele frequencies suggest that strong balancing selection at this locus occurred during the evolution of modern humans.
Our ancestors–the ancestors of all humans–ate each other so often that they actually evolved resistance to prion diseases.
Of course, they weren’t necessarily hunting each other for the calories (humans are not a very good source of calories compared to other common food sources.) They might have just had a habit of eating the dead from their own communities–which is still pretty gruesome.
Of course, cannibalism didn’t stop when people adopted agriculture. The Aztecs were cannibals“Indigenous Culture Day” celebrates genocidal cannibals who were even worse than Columbus. The Anasazi were cannibals. The word “cannibal” itself comes from the language of the Carib Indians. And of course, there are still-living folks in many other parts of the world who have cannibalized others.
But the idea that ancient humans were some kind of angels is absurd.