It's self-evident that this must be so. As an evolutionary strategy it's essential to produce a family before engaging in high risk activity like war or space e

It's self-evident that this must be so. As an evolutionary strategy it's essential to produce a family before engaging in high risk activity like war or space exploration that has a good chance of getting you dead. In the past for many if not all human cultures, most marriageable men that weren't set to inherit had to spend some time doing dangerous things before they had the social standing to marry.