@SteveJohnson By the same token, promiscuous men with no desire for family would be the dominant male genotype. I'd say it's more complicated than that. Human offspring needs years of upbringing to thrive, and by choosing the right moment to have children (which is in itself a different and interesting topic), responsible people can actually increase the probability of having thriving offspring. Or so I like to think. I don't believe this was measured in any way though.