FitzRoy undertook the second voyage of "Beagle" to return the surviving three Fuegians, at considerable personal expense. He was accompanied by Charles Darwin, who by the end of the voyage had become famous in scientific circles as a result of the discoveries he made during it, and who also collected much of the material that was to underpin his evolutionary theories during these travels. Decades later, following the publication of "The Origin of Species", FitzRoy – a committed Christian – regretted that he had facilitated Darwin’s research.