Why does egalitarian society has a lower density of men in the community?

I could explain the opposite claim: a non-egalitarian society typically has a higher density of men. This is caused by the regular killing of female babies: when a family can afford only one child, they would choose to raise only a boy.

In an egalitarian society this is not the case, and hence female children are not killed (any more then male chilredn) - so it would have a higher density of men.