Chimp Change: Did an HIV-like virus ravage early chimps?

Two million years ago, chimpanzees experienced a drastic loss of variability in certain genes that help them fight viruses, a new study reports. Widespread infection with an HIV-like virus may have pruned from the species individual chimps with some of these immunity genes, the study’s authors hypothesize. Ironically, the change could have conferred AIDS resistance on modern chimpanzees.