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http://www.timesonline.co.uk/tol/news/science/biology_evolution/article6922057.ece
November 19, 2009
Brain-eating tribe enriches understanding of mad cow disease
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Mark Henderson, Science Editor
* 11 Comments
Recommend? (3)
A cannibalistic ritual in which the brains of dead tribespeople were eaten by their relatives has triggered one of the most striking examples of rapid human evolution on record, scientists have discovered.
In the middle of the 20th century the Fore tribe of the Eastern Highlands province of Papua New Guinea was devastated by a CJD-like disease called kuru, which was passed on by mortuary feasts in which the brains of the dead were consumed.
Although the practice was banned in the 1950s and kuru has disappeared, it has left an imprint on the tribe’s DNA. Research has now identified a genetic mutation unique to the Fore that protects against the brain disease and which has spread swiftly through the population by natural selection.
As the mutation confers high or almost complete resistance to kuru, carriers have a survival advantage and have had more descendants. About 8 per cent of people from the Purosa Valley region, where kuru hit hardest, now have the gene, which is unknown anywhere else in the world.
Related Links
* Daniel Gajdusek
* New wave of mad cow disease feared
* What the cannibals taught us
The findings, from a team led by Simon Mead, of the Medical Research Council Prion Unit at University College London, show how quickly human evolution can respond to new environmental pressures.
They are described today in The New England Journal of Medicine as scientists prepare to celebrate the 150th anniversary of the publication of Charles Darwin’s On the Origin of Species on Tuesday.
Professor John Collinge, the director of the prion unit, said: “It’s absolutely fascinating to see Darwinian principles at work here. This community of people have developed their own biologically unique response to a truly terrible epidemic. The fact that this genetic evolution has happened in a matter of decades is remarkable.”
The research is also significant because it promises to shed light on the rogue prion proteins that cause Creutzfeldt-Jakob disease (vCJD), the human form of mad cow disease.
Dr Mead said: “It isn’t going to lead to a drug tomorrow but it would improve our background understanding of how prion diseases work and how they might be prevented.”
Oral histories provided by elderly members of the Fore tribe suggest that kuru emerged in the early 20th century and developed into a serious epidemic with an annual mortality rate of more than 2 per cent in some villages.
It mainly affected women and children, who would eat the remains of dead relatives. Kuru disappeared when cannibal rituals were stopped in the 1950s under the influence of missionaries.
In the new study scientists analysed the DNA of more than 3,000 people from affected and unaffected parts of the Eastern Highlands, including 709 who had taken part in cannibalistic rituals and 152 who had died of kuru.
The variant in the prion protein gene, called G127V, appears to have emerged about 1800 and then became advantageous with the arrival of kuru.
Dr Mead said that the variant would have spread rapidly for two reasons: “First, if you’re a carrier you’re resistant to the disease. More subtly, it also had benefits in terms of the relatives eaten. If you were in a family protected against kuru and ate auntie’s brain you were less likely to be eating an infected brain.”
In the genes
Sickle-cell anaemia This genetic disease is more common among African and Mediterranean people because the gene responsible also confers resistance to malaria
Blood groups People with blood group O are more vulnerable to cholera but less susceptible to malaria, spread by mosquitoes
HIV There is evidence that a variant of a gene called CCR5-32, which offers resistance against HIV, is increasing in frequency in Africa
Lactose tolerance Common in ethnic groups with a strong pastoral tradition such as North Europeans and East Africans
Skin colour Natural selection favours dark skins at equatorial latitudes for cancer protection, but pale skins at high latitudes, because they allow greater production of vitamin D
Source: Times database
November 19, 2009
Brain-eating tribe enriches understanding of mad cow disease
wait 2 secs to reload the image
Mark Henderson, Science Editor
* 11 Comments
Recommend? (3)
A cannibalistic ritual in which the brains of dead tribespeople were eaten by their relatives has triggered one of the most striking examples of rapid human evolution on record, scientists have discovered.
In the middle of the 20th century the Fore tribe of the Eastern Highlands province of Papua New Guinea was devastated by a CJD-like disease called kuru, which was passed on by mortuary feasts in which the brains of the dead were consumed.
Although the practice was banned in the 1950s and kuru has disappeared, it has left an imprint on the tribe’s DNA. Research has now identified a genetic mutation unique to the Fore that protects against the brain disease and which has spread swiftly through the population by natural selection.
As the mutation confers high or almost complete resistance to kuru, carriers have a survival advantage and have had more descendants. About 8 per cent of people from the Purosa Valley region, where kuru hit hardest, now have the gene, which is unknown anywhere else in the world.
Related Links
* Daniel Gajdusek
* New wave of mad cow disease feared
* What the cannibals taught us
The findings, from a team led by Simon Mead, of the Medical Research Council Prion Unit at University College London, show how quickly human evolution can respond to new environmental pressures.
They are described today in The New England Journal of Medicine as scientists prepare to celebrate the 150th anniversary of the publication of Charles Darwin’s On the Origin of Species on Tuesday.
Professor John Collinge, the director of the prion unit, said: “It’s absolutely fascinating to see Darwinian principles at work here. This community of people have developed their own biologically unique response to a truly terrible epidemic. The fact that this genetic evolution has happened in a matter of decades is remarkable.”
The research is also significant because it promises to shed light on the rogue prion proteins that cause Creutzfeldt-Jakob disease (vCJD), the human form of mad cow disease.
Dr Mead said: “It isn’t going to lead to a drug tomorrow but it would improve our background understanding of how prion diseases work and how they might be prevented.”
Oral histories provided by elderly members of the Fore tribe suggest that kuru emerged in the early 20th century and developed into a serious epidemic with an annual mortality rate of more than 2 per cent in some villages.
It mainly affected women and children, who would eat the remains of dead relatives. Kuru disappeared when cannibal rituals were stopped in the 1950s under the influence of missionaries.
In the new study scientists analysed the DNA of more than 3,000 people from affected and unaffected parts of the Eastern Highlands, including 709 who had taken part in cannibalistic rituals and 152 who had died of kuru.
The variant in the prion protein gene, called G127V, appears to have emerged about 1800 and then became advantageous with the arrival of kuru.
Dr Mead said that the variant would have spread rapidly for two reasons: “First, if you’re a carrier you’re resistant to the disease. More subtly, it also had benefits in terms of the relatives eaten. If you were in a family protected against kuru and ate auntie’s brain you were less likely to be eating an infected brain.”
In the genes
Sickle-cell anaemia This genetic disease is more common among African and Mediterranean people because the gene responsible also confers resistance to malaria
Blood groups People with blood group O are more vulnerable to cholera but less susceptible to malaria, spread by mosquitoes
HIV There is evidence that a variant of a gene called CCR5-32, which offers resistance against HIV, is increasing in frequency in Africa
Lactose tolerance Common in ethnic groups with a strong pastoral tradition such as North Europeans and East Africans
Skin colour Natural selection favours dark skins at equatorial latitudes for cancer protection, but pale skins at high latitudes, because they allow greater production of vitamin D
Source: Times database
