As the number of (captive) chimps analyzed has increased the width of the confidence interval has decreased.
In the January 18, 2002 issue of Science, Hahn and Shaw reported the first chimp in the wild detected to have an SIV infection. Anne-Mieke Vandamme of the Rega Institute in Belgium headed a group dating the virus using other techniques and concluded that a transfer from animals to humans occurred around 1675 with a confidence interval of between 15.
HIV-2 was first identified among patients in Cameroon in 1985.
HIV-1 was discovered by Luc Montagnier and his associates at the Institute Pasteur in Paris in 1983.
HIV-2 is more similar to SIV (Simian Immunodeficiency Virus) than is HIV-1 and it is much less virulent (usually not resulting in full blown epidemic sprung unannounced upon the world in the early eighties, the oldest verified case dates back to 1959 in Zaire.
A blood sample of an anonymous man was discovered in the archives of a Zairian (which was then called Congo) STD clinic in Kinshasa and analyzed in 1998 to establish this record.
Antibodies to SIV were found in the victims' blood samples.
They also analyzed blood samples of nearly 400 monkeys and baboons to assess the degree to which their antibodies bind to HIV.18% of the samples exhibited strong binding and another 14% showed less strong binding.There is even one case dating back to 1934 that is suspected, but not verified for lack of tissue and/or blood samples. reported the results of a phylogenetic statistical analysis of the evolution of the retroviral genome of HIV using complex mathematical models allowing for both constant and variable rates of evolution.Her group's analysis required the use of parallel supercomputers to backtrack the evolution to its source from monkeys (the chimpanzee species, Pan troglodytes troglodytes to be exact.).The computed model correctly placed the genome of the 1959 case on an evolutionary tree.The model estimates based on the latest data set the most reliable time of origin of the disease in humans as somewhere around 193115.