The majority of HIV researchers agree that HIV evolved at some point from the closely related simian immunodeficiency virus (SIV), and that SIV or HIV (post mutation) was transferred from non-human primates to humans in the recent past (as a type of zoonosis).Research in this area is conducted using molecular phylogenetics, comparing viral genomic sequences to determine relatedness.Orrorin lived about 6 million years ago, while Ardipithecus remains have been dated to 5.8-4.4 million years ago.At present, the vote is still out as to whether any of these three primates were in fact true hominins and if they were our ancestors.
While various sub-groups of the virus acquired human infectivity at different times, the global pandemic had its origins in the emergence of one specific strain – HIV-1 subgroup M – in Léopoldville in the Belgian Congo (now Kinshasa in the Democratic Republic of the Congo) in the 1920s.
The classification of Sahelanthropus has been the most in question.
The earliest australopithecines very likely did not evolve until 5 million years ago or shortly thereafter (during the beginning of the Pliocene Epoch) in East Africa.
Some apes occurring within that time period, such as Ramapithecus, used to be considered as hominids, and possible ancestors of humans.
Later fossil finds indicated that Ramapithecus was more closely related to the orang-utan, and new biochemical evidence indicated that the last common ancestor of hominids and apes occurred between 5 and 10 million years ago, and probably in the lower end of that range (Lewin 1987).