Upon Charles Darwin's return to England, at the end of the voyage of the HMS Beagle in October 1836, no unifying principles or theoretical framework provided an explanation for his and other naturalists’ diverse observations. Within a few months, he farmed out hundreds of specimens collected during the voyage to experts for identification. Having many of the Galapagos finches and Patagonian fossil mammals identified as new species challenged him to provide an explanation. His private transmutation notebooks (the Red, B and D, which were completed by September 1838) contain his first notations about the mechanism of natural selection (i.e. modern evolution). Darwin’s real triumph, thus, was his refusal to accept supernatural or metaphysical explanations for evolution. He remained rooted in the real, physical world.