"This geographically expansive account of the rise of evolutionary theory traces the lives and travels of four titans of 19th-century biology: [Charles] Darwin, the botanist Joseph Hooker, the physiologist Thomas Huxley, and Alfred Russel Wallace, a fearless globetrotter whose dangerous and often unpleasant journeys in the Amazon and the Malay Archipelago were the source of biological epiphanies and tens of thousands of specimens.... [Iain] McCalman's central conceit—that the four naturalists, who all traveled at length in the Southern Hemisphere, share 'a special bond of the "salt"'—supplies a fresh, antipodean perspective. McCalman evokes the physical hardships and social intricacies navigated by his heroes—flammable ships, uncooperative captains, and, on Antarctica, 'legions' of penguins so dense they could be breached only by 'kicking them to right and left'—and also the feel of an era when 'adventure and science went hand in hand'."—The New Yorker