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The process of evolution has helped people living in urban areas become immune to some serious diseases, research has suggested.
Resistance to conditions such as leprosy and tuberculosis has been acquired by people who have a history of living in more populated areas, because they are more likely to have a defensive genetic variant, a study found.
Ancient cities were ideal breeding grounds for the spread of disease because of poor sanitation and high population densities.
However, scientists discovered that disease resistance spread through populations because past exposure to pathogens was passed through the generations.
Dr Ian Barnes, from the School of Biological Sciences at Royal Holloway, said: “This seems to be an elegant example of evolution in action.
“It flags up the importance of a very recent aspect of our evolution as a species, the development of cities as a selective force. It could also help to explain some of the differences we observe in disease resistance around the world.”
Researchers analysed DNA samples from populations across Europe, Asia and Africa and compared rates of genetic disease resistance with urban history.
They found that in the areas with a long history of urban settlements, today’s inhabitants were more likely to possess the DNA variant which provides some resistance to infection.
The study, which was conducted by researchers at Royal Holloway, the University of London, University College London and Oxford University, is published in the journal Evolution.
Copyright Press Association 2010