J. theor. Biol. (1975) 53, 205-214 Mate Selection-A Selection for a Handicap AMOTZ ZAHAVI Institute for Nature Conservation Research, Faculty of Life Sciences, The George S. Wise Centre for Life Sciences, Tel-Aviv University, Israel (Received 23 July 1974, and in revisedform 2 December 1974) It is suggested that characters which develop through mate preference confer handicaps on the selected individuals in their survival. These handicaps are of use to the selecting sex since they test the quality of the mate. The size of characters selected in this way serve as marks of quality. The understanding that a handicap, which tests for quality, can evolve as a consequence of its advantage to the individual, may provide an explanation for many puzzling evolutionary problems. Such an inter- pretation may provide an alternative to other hypotheses which assumed complicated selective mechanisms, such as group selection or kin selection, which do not act directly on the individual. In his theory of sexual selection, Darwin (1874) tried to explain the evolution of characters such as the antlers of deer, the tail plumes of the peacock, the brilliant colouration of many birds and their fantastic displays and songs, by the cumulative effect of females preference for certain male types. He suggested that the disadvantages to male survival induced by such characters, are compensated for by more or better females preferring that individual to other males. But Darwin could not satisfactorily explain why females should prefer certain males. He just assumed that they prefer certain male types to others. The theory of sexual selection aroused and still arouses much debate. There is a basic difficulty to be explained. On the one hand, it is a common observation that the most beautiful males of a bird species, or the deer with the largest antlers, are preferred by females, and, on the other hand, there is no simple explanation to suggest in what ways the preferred males should be of better quality than others. Wallace (1889), therefore, dismissed altogether the theory of sexual selection by mate preference while others, like Poulton (1890), defended it. Fisher (1930) suggested that initially there was a correlation between the character preferred by the female and the quality of the male. This correlation when appreciated by discriminating females can account for the initial 205