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Ancient urbanization 'spurred evolution of immune system'


November 9, 2010 - Washington

It is due to previous exposure to infection in early cities that people are more disease resistant now, a new study has suggested.

"If cities increase the amount of disease people are exposed to, shouldn't they also, over time, make them natural places for disease resistance to evolve?" National Geographic News quoted study co-author Mark Thomas, a biologist at University College London, as asking.

The basic evolutionary theory: People who survive infection stand a better chance of having children and passing along disease-resistant genes.

Ian Barnes, study co-author and a molecular paleobiologist at University College London, screened DNA samples from 17 groups long associated with particular regions of Europe, Asia, and Africa-for example Anatolian Turks and the southern Sudanese.

Barnes analysed the DNA samples for a gene associated with resistance to tuberculosis (TB) and suspected of being associated with resistance to leprosy as well as to leishmaniasis, a reaction to sand fly bites, and to Kawasaki disease, a childhood ailment that involves inflamed blood vessels and can lead to heart disease.

In areas of ancient urbanization, it turned out, "we found very high frequency" for the TB-resistance gene, said Thomas.

The findings were published online by the journal Evolution.

ANI

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