Following the voyage of the "Beagle", Darwin had at his disposal a considerable collection of specimens and, on 29 October 1836, he was introduced by Charles Lyell to Owen, who agreed to work on fossil bones collected in South America. Owen's subsequent revelations, that the extinct giant creatures were rodents and sloths, showed that they were related to current species in the same locality, rather than being relatives of similarly sized creatures in Africa, as Darwin had originally thought. This was one of the many influences that led Darwin later to formulate his own ideas on the concept of natural selection.