Earlier quoted context omitted.
When sex started to be fun!
Oh. So, the 1960s, then.
Recreational sex is a basic human thing, across cultures and across history. People who think otherwise are just demonstrating ignorance of history and culture. This is common among young people, who often aggrandize themselves by convincing themselves that they are the first people ever to discover [insert basic human thing here]. Much harm has come out of their activities. (Though this too is a basic human thing, and much fun has also come of it.)