In his review of the republication of James Hutton's 1794 book An Investigation of the Principles of Knowledge and of the Progress of Reason, from Sense to Science and Philosophy, Paul N. Pearson (Nature 425, 665; 2003) tells us that Hutton devoted an entire chapter to natural selection, and adds, “it seems possible that a half-forgotten concept from his [Darwin's] student days resurfaced afresh in his mind as he struggled to explain the observations of species and varieties compiled from the voyage of the Beagle”.

Pearson is surely right. But despite his lifelong interest in natural history, Darwin was educated not as a biologist, but as a country vicar. Although he may have read Hutton's book, it is equally likely that Darwin read one of the standard religious works of his day (now perhaps the most ridiculed book in biology), William Paley's Natural Theology (1803), which presents Paley's proof of the existence of God, as well as of Divine creation.

Part of chapter five is devoted to what we would recognize as variation and selection. It begins, “There is another answer which has the same effect as the resolving of things into chance.” Paley proposes that “the eye, the animal to which it belongs, every plant, indeed every organized body which we can see, are only so many out of the possible varieties and combinations of being which the lapse of infinite ages has brought into existence; that the present world is the relict of that variety; millions of other bodily forms and other species having perished, being by the defect of their constitution incapable of preservation, or of continuance by generation.” As Pearson has commented, Stephen Jay Gould discusses this in his Structure of Evolutionary Theory (Harvard Univ. Press, 2002).

Of course, Paley proposes natural selection only to reject it. Nevertheless, it is there. And Darwin himself could not have expressed it better. Natural selection was a heresy in Darwin's day, but a common one.