Research involving a former brain-eating tribe from Papua New Guinea is helping scientists better understand mad cow disease and other so-called prion conditions and may also offer insights into Parkinson’s and dementia.

People of the Fore tribe, studied by scientists from Britain and Papua New Guinea, have developed genetic resistance to a mad cow-like disease called kuru, which was spread mostly by the now abandoned ritual of eating relatives’ brains at funerals.

Experts say the cannibalistic practice led to a major epidemic of kuru prion disease among the Fore people, which at its height in the late 1950s caused the death of up to 2% of the population each year.

In findings published in the scientific journal Nature, the researchers said they had identified the specific prion resistance gene – and found that it also protects against all other forms of Creutzfeldt-Jakob disease (CJD).

“This is a striking example of Darwinian evolution in humans, the epidemic of prion disease selecting a single genetic change that provided complete protection against an invariably fatal dementia,” said John Collinge of the Institute of Neurology’s prion unit at University College London, which co-led the work.

Prions are infectious agents that cause often fatal brain diseases such as CJD in humans, scrapie in sheep and BSE (bovine spongiform encephalopathy, or mad cow disease) in cattle.

They are also a rare but important cause of dementia, and scientists say it is now recognised that the process involved in these diseases – in which prion proteins change shape and stick together to form polymers that damage the brain – is also what happens in common dementias such as Alzheimer’s, and in Parkinson’s and other neurodegenerative diseases.

Collinge said his team was now conducting more studies to understand the molecular basis of this effect, hoping to find clues on the seeds of other misshapen proteins that develop in the brain and cause the common forms of dementia.

Worldwide, about 47.5 million people have dementia and there are 7.7 million new cases every year, according to the World Health Organization.

The total number of cases is projected to reach 75.6m in 2030 and to almost triple by 2050 to 135.5m.