SSS 2010-09-27（在线收听）

This is Scientific American’s 60-Second Science, I’m Christopher Intagliata. Got a minute?

City living has obviously influenced human culture—as have often been noted, how you gonna keep ‘em down on the farm after they’ve seen Paree'? But urban life may have also influenced human genes, making the descendants of ancient city dwellers more resistant to disease. That's according to a study in the journal Evolution.

The researchers started from the premise that densely populated cities would be good places for infectious diseases, which could spread easily from person to person. That situation should have set up selection pressure for the ability to survive such infections.

The scientists sampled the DNA of 17 populations from Africa, Asia and Europe, including longtime urbanites—like Italians, Turks and Iranians—and traditionally rural or nomadic groups, like Malawians or the Saami people of northern Scandinavia.

Then the researchers zeroed in on a gene variant that offers protection against diseases like tuberculosis or leprosy. After controlling for any shared ancestry between the groups, they indeed found that the protective gene was significantly more common in cultures with a long history of urban settlement. Which may be some comfort next time someone's sneezing near you on the subway.