In tests on macaque monkeys, the vaccine produces potent antibodies that disable a variety of HIVstrains from around the world, something previous vaccines have generally failed to do.
Mr Quammen traces the various strains of HIV back to the beginning of the 20th century, when the virus is likely to have moved from a chimpanzee into a human.
Unlike the widespread HIV-1 M strain, and the much rarer N and O strains, which jumped to people from chimpanzees, the newly described P strain originated in gorillas.