[div class=attrib]From Scientific American:[end-div]

Cities reverberate through history as centers of civilization. Ur. Babylon. Rome. Baghdad. Tenochtitlan. Beijing. Paris. London. New York. As pivotal as cities have been for our art and culture, our commerce and trade, our science and technology, our wars and peace, it turns out that cities might have been even more important than we had suspected, influencing our very genes and evolution.

Cities reverberate through history as centers of civilization. Ur. Babylon. Rome. Baghdad. Tenochtitlan. Beijing. Paris. London. New York. As pivotal as cities have been for our art and culture, our commerce and trade, our science and technology, our wars and peace, it turns out that cities might have been even more important than we had suspected, influencing our very genes and evolution.

Cities have been painted as hives of scum and villainy, dens of filth and squalor, with unsafe water, bad sanitation, industrial pollution and overcrowded neighborhoods. It turns out that by bringing people closer together and spreading disease, cities might increase the chance that, over time, the descendants of survivors could resist infections.

Evolutionary biologist Ian Barnes at the University of London and his colleagues focused on a genetic variant with the alphabet-soup name of SLC11A1 1729+55del4. This variant is linked with natural resistance to germs that dwell within cells, such as tuberculosis and leprosy.

The scientists analyzed DNA samples from 17 modern populations that had occupied their cities for various lengths of time. The cities ranged from Çatalhöyük in Turkey, settled in roughly 6000 B.C., to Juba in Sudan, settled in the 20th century.

The researchers discovered an apparently highly significant link between the occurrence of this genetic variant and the duration of urban settlement. People from a long-populated urban area often seemed better adapted to resisting these specific types of infections — for instance, those in areas settled for more than 5,200 years, such as Susa in Iran, were almost certain to possess this variant, while in cities settled for only a few hundred years, such as Yakutsk in Siberia, only 70 percent to 80 percent of people would have it.

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[div class=attrib]Image courtesy of Scientific American.[end-div]