By the time Darwin returned from the "Beagle" survey expedition in 1836, he had begun to doubt Lyell's ideas about the permanence of species. He continued to be a close personal friend, and Lyell was one of the first scientists to support "On the Origin of Species", though he did not subscribe to all its contents. Lyell was also a friend of Darwin's closest colleagues, Hooker and Huxley, but unlike them he struggled to square his religious beliefs with evolution. This inner struggle has been much commented on. He had particular difficulty in believing in natural selection as the main motive force in evolution.