It is not the business of evolutionary psychiatry to adopt moralistic attitudes to the phenomena it describes, but to make human behaviour, and its disturbances, comprehensible in evolutionary terms. In the past, psychiatrists have discussed reproductive disorders under such headings as sexual perversions or sexual deviations, using a tone of clipped disapproval to indicate that they, like their readers, will find the whole subject distasteful and one to be passed over as quickly as possible. Evolutionary psychiatry cannot indulge in such cursory condescension, since it regards reproductive success as the ultimate goal of human behaviour. Variations in reproductive behaviour must, therefore, be a primary focus of our study.