Evolutionary approaches to sexually transmitted infections.

Evolutionary approaches are particularly valuable for studies of sexually transmitted diseases. Methods for tracing evolutionary phylogenies have powerful new applications that use genetic data to trace the history of pathogens across millions of years, within outbreaks lasting years, and even within individuals. Equally valuable are less widely appreciated evolutionary methods for analyzing how host-pathogen co-evolution shapes extreme traits whose costs can be substantial. These and other applications of Darwinian medicine will improve understanding and treatment of sexually transmitted diseases.