As we know, HIV, Human Immunodeficiency Virus, is an incurable disease. HIV has multiple ways of transmitting itself by means of blood transmission, breast feeding, sexual intercourse and blood product.
These are the ways of HIV transmission, not the ways of HIV creation . Yes. Have anyone wonder how HIV is produced? haha...
One interesting fact about HIV - HIV is only created by baboons.
So, according to Charles Darwin, humans are evolution of apes. Therefore, the HIV virus is in the human's family tree and past down over centuries till today.
But what if Charles Darwin is wrong. Many oppose the theory of evolution. So for people who do not believe in Darwin, the simple explanation on how humans got affected goes something like this - one point in life, one human must have had sex with a baboon