Sexual selection and the evolution of morality

Abstract

In this thesis I discuss the Sexual Selection for Morality (SSM) hypothesis, which seeks to explain the evolution of morality in terms of sexual selection and costly signalling. The first part of the thesis puts SSM on the table for critical dissection. My starting point is the work on sexual selection, costly signalling, and morality by evolutionary psychologist Geoffrey Miller. I clarify and elaborate upon Miller's views by drawing on recent work in signalling theory. The result is a clearer and more nuanced version of SSM. In the second part of the thesis, I evaluate the empirical evidence for this revised version of SSM. I first clarify the predictions of the hypothesis, then survey relevant literature from biology, psychology, anthropology, and economics. Findings from these fields combine to support the claim that moral behaviour plays a signalling role. However, it appears likely that such signals are aimed at many receivers in addition to potential mates, including potential social allies as well as sexual and social rivals. SSM should thus be seen as part of a more general signalling-based account of morality. The third and final part of the thesis considers the metaethical implications of the truth of SSM. A relatively recent arrival on the metaethical scene is the Darwinian debunker, who claims that an evolutionary explanation of morality is, broadly speaking, undermining of morality. A prominent line of reply has been to claim that the fact (if it be one) that human morality is an adaptation shaped by selection over many millennia provides reason to think that our faculty for making moral judgements is likely to mostly produce true judgements. I call this the reliabilist reply. If SSM is true, I argue, then not all the conditions required for the success of the reliabilist reply are met. In particular, what I call the tracking condition fails to be met. The truth of SSM thus counts against the plausibility of the reliabilist reply and lends support to Darwinian debunkings of morality.