Over a lifetime spent outdoors, including years cataloging specimens throughout the Amazon basin and Malay Archipelago, 19th-century naturalist Alfred Russel Wallace reached the staggering conclusion that variation within animal species stemmed from adaptive changes that ensured the species' survival. In 1858, Wallace posited his idea to another scientist who, coincidentally, had recently reached the same independent conclusion: Charles Darwin. While the humble naturalist never gained Darwin's renown, Wallace left an impressive legacy as an explorer and specimen collector. Wallace's extensive travels and his life's work are celebrated alongside magnificently detailed and informative digital illustrations in Darwin's Rival, Christiane Dorion (Into the Forest) and Harry Tennant's engrossing oversized picture book for curious young environmentalists. --Kit Ballenger, youth librarian, Help Your Shelf