Sexual selection and the role of parasites

Six years ago, William Hamilton and Marlene Zuk¹ proposed a novel and - on the face of it - bizarre explanation for the evolution of secondary sexual characters. Contrary to most theories of sexual selection through female choice², Hamilton and Zuk suggested that the bright colours and elaborate ornaments of many animal species have a utilitarian function: they allow females to assess a potential mate's ability to resist parasites. Recently, several studies have begun to test the hypothesis directly, and the idea has been discussed at two meetings^3,4. Here I review the work to date, and discuss the difficulties involved in gathering and interpreting the evidence still required.