The biological adaptation of the human male to be capable of reproduction early & often (for survival), seems to be waaay stronger than a couple thousand years of social conditioning to postpone it... or else we'd be seeing age of puberty *rising* in response to the successful survival of those individuals who adapted. I don't have an answer either. I suppose start by looking for a high-functioning homogeneous society (past or present) and take a look how they approached it.