Humans and baboons share similar evolutionary histories and environments in the East African savanna. Parallel evolution has also been demonstrated in how variation of the Duffy gene affects their respective resistance or susceptibility to infection by malaria parasites. The mechanism is well-known in humans: when the Duffy gene is on, it builds receptors on the surface of red blood cells allowing malaria parasites to land. When the gene is off--there is no infection.

In baboons--there is also a definite link from genetic variation to degree of infection by a malaria-like parasite, but the mechanism is less clear. When the gene is on, more receptors are built, but the incidence of infection is also lower. When the gene is off, the opposite is true. Read more about this research at nsf.gov/news/news_summ.jsp?cntn_id=115048.