Fun fact, our DNA contains lots of ancient virus DNA. Some of it can make proteins that resemble HIV components.

https://en.wikipedia.org/wiki/Endogenous_retrovirus

So where did HIV come from? Who knows. It( not the current version of HIV, something similar) has been with us for millions of years in 1 form or another. Enough to leave a large mark on what makes us, us, our DNA.