Redpill me on HIV.
According to picrelated, there exist two theories as for its origin. The first is that it developed naturally, but the author notes that there's no reason why it hasn't over the past few hundreds years. The second suggests that incompetence (albeit I can't imagine doing so on this scale without coming across issues of this kind) in the Oral Polio Vaccine (OPV) mass effort in Africa lead to the mutation of the SIV. The reason why neither of the theories has been proven correct is because there's absolutely no evidence as for the first, whereas for the second it is due to possible vaccine hesitancy that would follow from it being proven.