I think our children are exposed to both at far to young an age now. If 12 yr olds are having sex/shooting people, in a world that is already overpopulated and with a very large share of problems, then something in society will probably shift on it's own.
In a situation where we were living in a tribal environment with small tribes, some of which would probably be nomadic, as soon as a woman was of childbearing age, she could be married. These days that is frowned upon as the girl is considered 'unready'. In our current environment that is very true. She would probably have to fend for herself or she would probably receive support from her family. In the days of tribes, the tribes would assist the young woman in how to raise the child, and would probably communally raise the children anyway. Young men would be taught to hunt, to go to war. How to fight how to build.
These things are considered redundant in our current day and age, yet they reach to the heart of what we are.
Why should children have to wait to experience them? They should learn the truth about human nature as early as possible to avoid disallusionment and naivety.