The year was 1848. a young British naturalist named Henry Walter Bates had gone to the Amazon with fellow countryman Alfred Russel Wallace to look for evidence of the origin of species. Over the course of his 11-year stay, he noticed that local relatives of a European butterfly known as the cabbage white—the pierids—were bedecked in the showy reds and yellows of rain forest butterflies called heliconids. Observing that the heliconids seemed to possess toxins that made them unpalatable to predators, Bates reasoned that by mimicking the toxic heliconids’ warning colors, the harmless pierids were escaping predation. When Bates returned to England in 1859, the year that Charles Darwin published On the Origin of Species, his discovery of these “mockers,” as he called them, became the first independent evidence to corroborate Darwin’s theory of evolution by natural selection—which holds that organisms best able to meet the challenges in their environment survive to produce the most offspring, so that their traits become increasingly common through the generations.
Apart from Darwin and Bates, though, most biologists were slow to recognize the significance of nature’s impersonators. But now, a century and a half later, mimicry is fast becoming a model system for studying evolution. It is ideally suited to this task because both the selection pressure (predation) and the traits under selection are clear. Indeed, mimicry demonstrates the process of evolution in its most stripped-down form. Discovery of new types of mimicry has also helped fuel fresh interest in the phenomenon among biologists. Joining the classic examples familiar from high school biology class—such as the scarlet kingsnake, whose coloring resembles that of the eastern coral snake, or the viceroy butterfly, whose wing pattern matches the monarch’s—are chemical, acoustic and even behavioral mimics. And stunningly, genetic analyses of one group of mimics have revealed a mechanism by which new species can arise.