Darwin's Sacred Cause: How a Hatred of Slavery Shaped Darwin's Views on Human Evolution

W ho can divine the intentions of the human heart, the mo­ tives that guide behavior? Some of the reasons for our actions lie on the surface of consciousness, whereas others are more deeply embedded in the recesses of the mind. Recovering motives and intentions is a principal job of the historian. For without some attribution of mental attitudes, actions cannot be characterized and decisions assessed. The same overt behavior, after all, might be described as " mailing a letter " or " fomenting a revolution. " The recovery of intentions is crucial for the historian's narrative. In the case of Charles Darwin, per­ haps the most important question is, What led him to formulate his theory of the modification and common de­ scent of species? Scholars have settled more or less securely on the answer, ar­ guing that since he was quite aware of the transmutational views of his grand­ father, Erasmus Darwin, and those of Jean­Baptiste Lamarck, Darwin would have had his eyes opened to the vari­ ability of species on his five­year Beagle voyage. After he returned to England in 1836, he consulted with John Gould, or­ nithologist at the British Museum, about three types of Galápagos mockingbirds. They were not, as the young natural­ ist had initially assumed, varieties of a single species that had adapted to local environments but true and good species. Frank Sulloway, some years ago, con­ vinced most of the scholarly community that Darwin's experience with Gould ignited a mind packed with possibility. Thereafter, wouldn't sheer scientific am­ bition, the excitement of getting to the bottom of things, have pushed Darwin along during the 20 years of the theory's gestation? Wouldn't he have been mo­ tivated by the same kind of desire for adventure and recognition that led him to depart England in the first place? It has been generally assumed that posi­ tive answers to these questions would account for Darwin's parting company with English scientific orthodoxy. In Darwin's Sacred Cause, Adrian Desmond and James Moore propose a radically new answer to the question of Darwin's motive in pursuing a theory of common descent. I confess that when they first sketched their answer in a long preface to their 2004 edition of Darwin's Descent of Man, I was unconvinced, and in a review for the British Journal for the History of Science, I explained why. They had argued that Darwin's militant …