The gorilla SIV, they found, had originated from chimpanzees. To better understand how gorilla SIV was related to viruses in chimpanzees and humans, Peeters and her colleagues set out to systematically gather gorilla stool from across their range as well. Searching through more than 3,000 samples of gorilla feces, they failed to find any gorilla SIV outside of Cameroon. But inside Cameroon, the story was different. They found more gorilla SIV. In 2015, Peeters and her colleagues announced that two of these new lineages of gorilla SIV were the ancestors of HIV-1 O and P,
