As Darwin did not believe that pure aesthetics would guide female peacocks and lions in their choice of mating partners, he had to find a rational reason for females’ preference for males with hindering characteristics. The very fact, he reasoned, that these features make life harder signals to prospective partners that individuals who can do reasonably well with them have an especially good genetic set-up and are thus likely to produce strong offspring.
达尔文认为，并非纯粹的美观引导雌孔雀或雌狮子去选择其配偶，因此他必须找出雌性动物偏爱具有阻碍性特征的雄性动物的合理原因。他推断，事实是，这些令生存更为艰难的特征向未来的配偶表明，能够合理地处理这些阻碍性特征的个体会拥有极好的遗传结构，因而可能产生强壮的后代。它们因此为雌性动物所偏爱。