listen to this at their website or read a transcript.
Experts think it was around 1930 that HIV got its big chance, give or take a decade. We know that because there viruses mutate at a constant rate. So scientists can clock how long ago HIV diverged from its chimpanzee ancestor.
The date is important because of what was going on in West Africa then. The French and Belgians were hell-bent to extract rubber and ivory.
(Soundbite of Cameroonian workers)
They conscripted workers, like these Cameroonians, recorded in 1954, to build the railways to ship their booty to the coast. Moore says this is how it might have happened.
Prof. MOORE: You have a rubber collecting crew coming into the village. The routine practice was to kill a few people as an example, or take their children hostage and kill them if the rubber didn't come in. So these patrols were avoided. And so you could have someone seeing the boat come upriver, flee into the forest, perhaps not very used to butchering chimpanzees, so he gets cut in the process of feeding himself and family in the forest.
KNOX: And get the virus that would become HIV. Then, he ventures into another village.
Prof. MOORE: He gets caught by a press gang getting workers for the railroad, taken down the hundreds of kilometers, arrives exhausted and hungry, and receives a whole series of injections along with everybody else in his group.
KNOX: With unsterilized syringes.
Prof. MOORE: So you've got a few hundred people injected probably with one or two needles.
KNOX: Syringes were expensive then. Handmade. In one campaign, French doctors used six syringes to inject 80,000 African workers with a medicine for sleeping sickness.
The horrors of colonial practices in Africa at the start of the twentieth century are well described in Joseph Conrad's book Heart of Darkness which, strangely, became the inspiration for much of the classic Vietnam war movie Apocalypse Now.
Villages which failed to meet the rubber collection quotas were required to pay the remaining amount in severed hands, where each hand would prove a kill. Sometimes the hands were collected by the soldiers of the Force Publique, sometimes by the villages themselves. There were even small wars where villages attacked neighbouring villages to gather hands, since their rubber quotas were too unrealistic to fill.