The pandemic strain of HIV-1 is closely related to a virus found in the chimpanzees, which live in the forests of the Central African nations.
Apparently the transmission of this virus was made between man and chimpanzee, and occurred during the late 19th or 20th century, in a time where urbanization and colonization in Equatorial Africa were massive.
So the locals, because they were forced out the rural area by the Europeans, because the Europeans needed resources, were not keen to pursue their agricultural way in the jungle, they turned to non domesticated meat as a way to survive, and the transmission occurred between bush-meat seller and chimpanzees right after those events, because those sellers were most of the time bit by the animals they were hunting and so on there were a blood exchange between the animal and the hunter that allowed the first strain of the virus to expand to our specie.
There is approximately 40 millions of people living with AIDS/HIV in this world, about 4 millions of them are children.
So don't be silly, and protect your willy !