[hrolfgar]

Sort of like the prisoners' dilemma; at the end of the day, the selfish actors will choose to locally optimize.

Btw, this argument about the sex ratio stabilizing at 1:1 is known as Fisher's principle. Fisher made another really interesting observation about how extremely exaggerated male ornamentation, like in peacocks, reaches its equilibrium when the aesthetic advantages from a large, attractive tail becomes offset by the practical costs of being slower, needing more food to produce said tail, being highly visible, etc. This one's called "Fisherian Runaway". These purely aesthetic traits will "run away" all the way up until they becoming detrimental to survival.