original_query: When did the zoonosis occur in equatorial Africa?
query: When did the zoonosis of HIV occur in equatorial Africa?
answer: Scientists estimate the jump from chimpanzee to human likely happened in the late 19th or early 20th century, a time of rapid urbanization and colonization in equatorial Africa.  More precise dating studies suggest a most recent common ancestor (MRCA) between 1915 and 1941, or even between 1873 and 1933, with central estimates around 1902 and 1921.