As in cities today, the earliest towns helped expose their inhabitants to inordinate opportunities for infection -- and today their descendants are stronger for it, a new study says. "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?" asked study co-author Mark Thomas, a biologist at University College London... study co-author Ian Barnes, 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...