Teenage sex, or even precocious sex, was not only prevalent before the invention of marriage, but it was better given that hormones are strongest when they first emerge because of how hedonism works.
Now before you go calling me a pedo, not everyone has precocious puberty. I was one of the unlucky few, but I'm a victim of the new-age more than most of you so I don't really care about opinionated opposition. 😛