haxxiy on 26 August 2013
Children should be obvious enough and for women, they are biologically more valuable than men. No, really.
Women sire issue one or two at a time and take a long time to do so while men can impregnate multiple females at a time. It's much easier for a population to thrive with excess females than excess males. Take into account non-monogamous mammals, with a functioning breeding hierarchy, the chances you are less important as a male, statistically speaking, are higher.
You could also argue those who made these rules were male themselves and perhaps unconsciously saw it as a way of curbing competition while preserving all these valuable females. Either way, the shadow of nature and evolutionary biology is still there.
