Tuesday, January 10, 2006

Are Prions A Defense Against Cannibalism?

An article in this week's Science throws doubt on a previous study that looked at whether modern humans retain a PRNP gene. It was thought that this genentic variation gave some protection against vCJD in cannibals.
n the first study, published in Science (25 April 2003, p. 640), a team led by John Collinge of University College London (UCL), looked at a human gene called PRNP which codes for prions (ScienceNOW, 10 April 2003). These misfolded proteins are thought to be responsible for several neurodegenerative diseases including Creutzfeldt-Jacob Disease (CJD) and kuru. Individuals with certain variations in this gene are more resistant to the diseases.

When the team looked at the chromosomes of more than 1000 people from populations around the world, they concluded that the prevalence of two of these variations was due to an evolutionary balancing act that had kept them in the gene pool for as long as 500,000 years. The researchers hypothesized that this "balancing selection" was due to widespread cannibalistic practices that had made early humans susceptible to prion diseases.

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