What is wrong with people.

Several studies have found that women prefer men their own age or slightly older, and men prefer women in their early 20s regardless of their own age. It’s not hard to explain that with evolutionary biology, as that’s when women are most likely to successfully bear children.

Of course evolutionary biology can explain behaviors like rape and dueling, which are serious crimes in modern societies.

Your “very young” might mean younger than early 20s though, and we do have a crime for that most places if the number gets low enough.