The evolution of female orgasm: adaptation or byproduct?

Do women experience orgasm because this trait was shaped by natural selection to augment female fitness? Or are women merely the lucky recipients of developmental patterns favored by selection to produce orgasm in males? A recent and widely publicized book by Elisabeth Lloyd (2005a) contends that there is insufficient evidence to validate any of the adaptive explanations yet proposed for female orgasm. We agree. But our reading of the data differs from Lloyd's. In this essay, we outline why, unlike Caton (2006), whose review of Lloyd's book appeared previously in this journal, we are not persuaded by Lloyd's argument that female orgasm is a nonadaptive byproduct of orgasm in men. We hold this view because we disagree with the criteria Lloyd uses to evaluate evolutionary hypotheses, and because we believe Lloyd defines female orgasm too narrowly, ignoring critical information about its affective aspects.