Competing theories on the aetiology of eating disorders originate from a diverse set of disciplines. One such discipline is Evolutionary Psychology which assumes that the human mind has been shaped by natural and sexual selection. Most evolutionary theories on eating disorders limit themselves to the causation of anorexia nervosa only. The Sexual Competition Hypothesis (SCH), based on the Darwinian theory of sexual selection, provides an explanatory framework for the whole spectrum of eating disorders. It contends that intense female intrasexual competition (ISC) is the ultimate cause of eating disorders. The SCH explains the phenomenon of the pursuit of thinness as an adaptation to ISC in the modern environment. It argues that eating disorders are pathological phenomena that arise from the mismatch between the modern environment and the inherited female adaptations for ISC.

To test predictions from a novel evolutionary hypothesis for eating disorders.

1. i) To examine the relationship between disordered eating behaviour (DEB) and ISC in a sample of female undergraduates.

2. ii) To establish whether there is any relationship between DEB and Life History (LH) strategy.

A group of 206 female undergraduates were recruited. A structural equation model was constructed to analyse the data.

ISC for mates was significantly associated with DEB, as predicted by the SCH. DEB was found to be predicted by fast LH strategy, which was only partially mediated by the SCH.

The results of this study are supportive of the SCH and justify research on a clinical sample.