Some very interesting papers have come out of Hahn’s laboratory in the past two decades, many of them published with a junior researcher as first author and Hahn in the mentorship position, last. That was the case in 1999, when Feng Gao produced a phylogenetic study of SIVcpz and its relationship to HIV-1. At the time there were only three known strains of SIVcpz, all drawn from captive chimps, with Gao’s paper adding a fourth. The work appeared in Nature, highlighted by a commentary calling it “the most persuasive evidence yet that HIV-1 came to humans from the chimpanzee, Pan troglodytes.”