A peacock grants a peahen one tiny favor: a batch of sperm and nothing else. He will not guard her from other peacocks, feed her, protect a food supply for her, help her incubate her eggs, or help her bring up the chicks. She will do all the work. Therefore, when she mates with him, it is an unequal bargain. She brings him the promise of a gigantic single-handed effort to make his sperm into new peacocks; he brings just the tiniest—though seminal—contribution. She could choose any peacock she likes and has no need to choose more than one. At the margin, he loses nothing and gains much by
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