PAUL D STEWART / SCIENCE PHOTO LIBRARY PAUL D STEWART / SCIENCE PHOTO LIBRARY
Darwin on sexual selection. Specimen of Darwin's beetle (Chiasognathus grantii) on the page with its illustration, from 'The Descent of Man, and Selection in Relation to Sex' (1871). Darwin collected this beetle species in Chile during the voyage of the Beagle. He noted the enlarged mandibles of the males were 'not so strong as to produce pain to finger'. He later used this beetle as an example of sexual adornment in his 1871 work. He thought that in addition to any aggressive role, they might be sexual adornment for display to rivals and to the less well-endowed females.
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