Catalogue number: Drawer 20
Wallace's specimens of butterflies showing colour differences between males and females.
Wallace arranged the specimens in this drawer to show the dramatic differences in colour between the males and females of some butterfly species. This is known as sexual dimorphism.
One of the most important issues on which Wallace and Darwin disagreed was the extent to which sexual selection could explain sexual dimorphism. Wallace thought that males might fight to compete for females, but did not think that females made any choices themselves. Wallace therefore believed that natural selection, and not female choice, was responsible for the evolution of sexual ornaments (such as attractive colours in butterflies). As such he claimed to be more Darwinian than Darwin himself! In fact the modern theory of sexual selection combines elements of both Wallace's and Darwin's views.
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View high resolution scans and transcripts of Alfred Russel Wallace's correspondence, including all surviving letters between him and Charles Darwin.