If one is looking just at the science of it all, sure one could make an argument for young adults, those that are still developing to reproduce.
But the would be irresponsible, IMO, since it ignores the societal environment of this country. A young person, under 18, generally lack the means to effectively raise a child and support a family. Protect them from themselves and give them a chance to maturely plan their life a bit, a 16 years old, let alone a 14 year old have no idea of where they want to go in this thing called life.
It also ignores the real issue. full grown adults preying on the youth for a quick roll in the hay. There comes the rub, where do you drawn the line to define an adult.. in most circumstances that is 18. Hence the age structure, however the states with a relative age clause have it more correct IMO. If they are within say 4 years of each other, I think little of it.. say a 17 year old hooking up with a 21 year old. Just better not be my daughter. ;)
I sorry, if you are a 30 year drone.. you have no business praying on a young adult under 18.
Why can't we argue the drinking age.. that is easy. π
"The oranges are dry; the apples are mealy; and the papayas... I don't know what's going on with the papayas!"