system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do STDs form/ where do the originate?

Everything I’ve seen just talks about how they spread but where did they come from?
gpt
STDs are just diseases.  At some stage in their evolution they mutated, maybe one branch of their family tree spread by making victims cough out particles and others spread by sexual contact.  There are pros and cons to each strategy, lots of coughs happen with nothing around and coughing people "seem sick" to their peers.  On the other hand, sex isn't as frequent as coughing.

The diseases we call STDs today evolved from the branches that spread by sex.  It's not a different disease concept, it's just a label humans put on STDs.