'Base of the Skull of Toxodon Platensis', South America, c 1832-1836.
© Science Museum / Science & Society Picture Library
Lithograph by George Scharf after his own drawing, from 'The Zoology of the Voyage of HMS Beagle', published in London, 1839-1843, and edited by the British originator of evolutionary theory Charles Darwin (1809-1882). The extinct Toxodon was related to horses and tapirs. Its remains have been found in Pliocene and Pleistocene deposits in South America. Darwin was naturalist on 'HMS Beagle' during its voyage of 1832-1836, the purpose of which was to make a scientific survey of the South American waters. Darwin's observations contributed to his discovery of the principle of natural selection of heritable variation as the cause of evolution. His most famous work, 'On the origin of species by means of natural selection', was published in 1859.