U nder w hat circumstances does an anim al becom e fitter because it displays? E volu tion is a process o f change; it occurs w hen new conditions create new needs and hence give advantage to new sorts o f individual. In the evolution o f courtship this means individuals w hose behaviour and appearance before m ating is stim ulating and attractive. T heir advantages m ust be such as to m ake fo r better survival o r m ore efficient reproduction (that is, they m ust be fitter). W h a t k ind o f needs could such individuals fulfil?