Some surveys reveal that a majority of couples who married in the post-war 1950's were either pregnant (and that's why they got married) or already having sex at the time of the wedding. So much for the idea that people in the past always abstained before the wedding night.
The entire concept of the nuclear two-parent family as the ideal is a recent invention, anyway. Even marriage is not quite as old or settled as many people think. Poor people have routinely lived together without formal ceremonies because there was no inherited property to pass on, so virginity and paternity were not as important. In the past, children were often raised communally, family was defined through the matrilineal side, and the mother's brother might be the main dude in the kid's life.
That's why this religious intrusion into where, how and with whom people live, and whether, when, and with whom they have sex, is so offensive. They devise rules and policies based on made-up, imaginary sh!t, and then try to force people to conform to their fabricated version of the world. If a majority of people won't or can't follow your social rules, maybe you have screwed-up rules.