Beyond the common pressure of starvation, men are under selective pressure to cooperate so as to not get wiped out by neighboring bands.
Think that through - do peahens inherit their fathers plumage? Are men under selective pressure for wide hips? Same genes, different morphology in males and females. Same for behaviors.
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Hips are a sex specific selective pressure on women. Women who have hips too narrow to give birth don't leave offspring. Cooperation, ability to get along with men in a war band is a selective pressure on men. Men who fail in that area die without offspring.
End of conversation
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