It is not generally known that when the Beagle departed the Galápagos on October 20, 1835, no fewer than sixteen diminutive natives of the islands were aboard, having befriended the young naturalist Charles Darwin. Renaming themselves after figures important in Darwin’s life, such as the embryologist Karl Ernst von Baer, the sixteen lived and worked with Darwin, even aiding him in the composition of his books. Extraordinarily long-lived, they eventually relocated to the United States, where they corresponded with the Harvard biologists Stephen Jay Gould, Ernst Mayr, and E. O. Wilson. They later returned to the Galápagos, where they are currently engaged in local conservation efforts.Such, at any rate, is the premise of Frank J. Sulloway’s Darwin and His Bears—and yes, the sixteen passengers, including Karl Ernst von Bear, are the bears of the title. Sulloway explains that the book began as a birthday present for a godson over 30 years ago and then “evolved … into a didactic fantasy” (p. 169). Familiar elements of children’s fiction are retained: the bears are gluttons (although for berries and bananas rather than honey and marmalade), sing amusing ditties, and engage in silly pastimes such as tortoise racing. But they are not clearly individuated (except in Appendix 1, which lists their habits, talents, and islands), and their ursine doings are not really the focus of the book.Instead, the bears provide the basis for Sulloway to recount pivotal episodes in Darwin’s career. A historian of science with important work on Darwin’s research in the Galápagos to his credit, he is a trustworthy guide in general. But his attempts to lever the bears into historical importance—suggesting, for example, that it was a bear who recommended Thomas Malthus’s essay on population to Darwin—are neither striking nor memorable. Chapter 7—in which a bear, intoxicated by gobbling berries sent to Darwin by Ernst Haeckel (hence haeckleberries), anticipates Freudian psychoanalysis—is self-indulgent: Sulloway is also the author of the pioneering study Freud, Biologist of the Mind (1979).The bears similarly provide the basis for Sulloway to describe the central results of the work of Darwin and the biologists at Harvard. The diversity of the bears across the Galápagos, for example, is explained in terms of “maternal berry selection and survival of the fattest” (p. 40). Later, a phylogenetic tree of bears is presented, which includes Pooh and Paddington as well as Darwin’s bears (in the “Smart Bears” clade): but where are Corduroy, the Berenstain Bears, Baloo, Rupert Bear, Larry, Irving, and Muktuk, to say nothing of the panserbjørn Iorek Byrnison? Unfortunately, in the later chapters, the jokes sometimes presuppose knowledge of the details of the scientific work that not all readers will possess.Darwin and His Bears was clearly a labor of love for Sulloway, who even prepared the abundant full-color illustrations himself. But it is likely to appeal primarily to people who are both already knowledgeable about the history and the science of evolution and have a taste for the type of humor, often forced, on display—a limitation shared with a comparably playful book by the late historian of science John C. Greene, The Wonderful Adventures of Nat Selleck & Eva Lou Shinn in Sci Fi Land (2007). Those in search of a humorous but accurate treatment of evolution suited for young readers will do better to look elsewhere, starting with Jay Hosler’s superb Evolution: The Story of Life on Earth (2011).