"Historians of biology," Bowler writes, "have ... tended to discuss the history of evolutionism as though it were essentially the history of Darwinism." But Darwinian theory, based on natural selection, was not the only mechanism offered during the 19th century to explain evolution. Bowler's readable but scholarly account takes the reader through the panoply of the evolutionary (but nonselectionist) ideas of such figures as Owen, Spencer, Kelvin, Huxley, Haeckel, and Freud.