Cannibalism is seen as one of the darkest taboos in many cultures. But beyond the social stigma of eating fellow humans, there's a strange (and fascinating) danger that comes with cannibalism.

In 1961, a young Australian medical researcher called Michael Alpers headed to the Eastern Highlands of Papua New Guinea, inspired to merge his two passions of medicine and adventure. Here, he began to investigate a mysterious condition suffered by the Fore people, a scarcely touched tribe that lived deep in the mountains and practiced cannibalism. 

“The body was eaten out of love as well as for gastronomic appreciation,” Alpers wrote in one of his academic texts about the Fore people.

They called this condition "kuru". Every year, kuru would kill up to 200 people of the tribe, sometimes in startling circumstances. Starting with tremors and an impaired ability to work, sufferers go on to develop a total loss of bodily function, depression, and often emotional instability, sometimes exhibiting itself as hysterical laughter. When word of the disease spread to the west, the media sensationally dubbed it “laughing death”. 

The Fore people believed it was a terrible curse, but Alpers wanted to find a more scientific explanation to this mystery. Curiously, the condition did not appear to be caused by a virus, bacteria, fungus, or parasite. Equally as strange, it was only women and children who fell sick.

This made the researchers begin to wonder: Perhaps it had something to do with the Fore’s funerary ritual of cannibalism. The practice involved only the women and children eating the brains, while the men would just eat the flesh. 

During an interview for Cosmos Magazine in April 2016, Alpers explained: “The argument for cannibalism – and I don’t use that term anymore, but it was used then – was compelling. Everything fitted.”

“Why did women and children get the disease? Because they were the ones that carried out the practice – the men didn’t. It explained why it was dying out in young children – because the [Australian patrol officers] had proscribed cannibalism. You could also conclude that the disease was not being transmitted vertically from mother to child.”

By 1966, Alpers and a team of other scientists were starting to catch on to the fact that kuru was caused by something other than a viral infection, a bacterial disease, or even genetics – it was actually caused by a puzzling agent called a prion. This discovery paved the way for Baruch S Blumberg and D Carleton Gajdusek to sweep up a Nobel Prize in Physiology or Medicine in 1976 for "their discoveries concerning new mechanisms for the origin and dissemination of infectious diseases."

Prions are essentially normal proteins that have become twisted and turned to the "dark side". These infectious agents lose their functions and acquire the ability to turn other normal proteins into prions too, thereby becoming infectious.

Some of the more infamous diseases caused by prions are BSE, aka “Mad Cow disease”, and its human alternative Variant Creutzfeldt-Jakob disease – two degenerative brain disorders that share an uncanny resemblance to kuru. It’s believed that BSE is most likely the result of cows eating the recycled offal and brain tissue of other cows, just like kuru.

So, eating human brains might not always be the best of ideas, even before you get into the whole array of blood-borne illnesses that you could contract, from HIV and hepatitis to E. coli and Ebola. However, here’s where the story takes a turn. A study published in Nature in 2015 found that the Fore people who regularly ate brains had developed a resistance to prion diseases, a discovery that is still helping scientists understand degenerative brain diseases, such mad cow disease, Creutzfeldt-Jakob disease, and some cases of dementia.