Were it not for a single base pair insertion/deletion mutation in the MMP3 gene sequence, the incidence of heart disease among modern Europeans would be much higher, according to the authors of a study published this week in Current Biology . But others cast doubt on the suggestion that the gene necessarily played such an important role.

"Our analyses show how positive natural selection can shape variation in a human population, because we exclude other possibilities, said lead author Matt Rockman , of Duke University. "For a long time, it's been argued that genetic variation underlying disease is the result of deleterious mutations. That is, there's a 'good' version of the gene but occasionally a 'bad' mutation arises that leads to disease susceptibility."