runaway hypothesis

The runaway selection hypothesis, proposed by R.A. Fisher, explains the rapid evolution of certain physical traits in male animals. This occurs when females strongly prefer males with exaggerated traits, such as elaborate plumage or courtship behaviors. In subsequent generations, female offspring inherit the preference for these traits, while male offspring are more likely to possess them. This can lead to extreme sexual dimorphism within a species. Examples include the long tail of the male African long-tailed widowbird and the complex songs of male European sedge warblers, where females favor males with the most pronounced expressions of these traits.1