What is the origin of STDs?

I have always wondered this. About a year ago I did some research, and I pretty much concluded someone was born with the disease, then "spread it" if you know what I mean.
The first time that any hospital treated STD's was in 1746. The first STD to begin being treated was syphilis. In the 1980's the first cases of AIDS were reported. Technically, gonorrhea is a bacterial STD. Bacteria has been around since the beginning of time, evolving into new and more complex versions.