The Human Immunodeficiency Virus, HIV, is a retrovirus that contains RNA as the genetic material. Scientists believe that the chimpanzee version of the immunodeficiency virus (called Simian Immunodeficiency Virus or SIV) was the original source of HIV infection in humans.
It is theorized that SIV was transmitted to humans and mutated into HIV when humans in Africa hunted chimpanzees for meat and exposed themselves to the infected blood. The mutation rate in retroviruses, including SIV and HIV, is much higher than it is among DNA viruses.
The MOST likely explanation for this is that