Last month, the Dr Pepper company posted an ad, “Evolution of Flavor,” on its Facebook page. That may be a new way to promote a beverage, but the ad harked back to a time-honored image: the “monkey-to-man” illustration that has become an iconic and instantly recognizable visual shorthand for evolution. In response, anti-evolutionists flooded the company’s website, protesting what they claimed was the soda company’s endorsement of Darwinism.
That a 150-year-old scientific illustration could trigger a political attack today speaks volumes about the contentious state of the American debate over evolution. But it also opens a window onto the extraordinary history of the image itself—one of the most intriguing, and most misleading, drawings in the modern history of science.
For all its familiarity, no one—not biologists, not creationists—thinks the monkey-to-man drawing is an accurate illustration of Darwinian evolutionary theory. Darwin’s “Origin of Species” (1859) contained only a single illustration: a branching diagram, depicting evolution as a complex process characterized by random events, which is roughly how scientists view evolution today. The first version of the classic image actually appeared in an 1863 book by English comparative anatomist Thomas H. Huxley, and recalled an older tradition presenting nature as a “chain of being.” Combining aspects of the new scientific theory with a way of thinking about humans familiar to Victorians, it suggested a logical, evenly paced progression that eventually arrived at the species that was evolution’s ultimate goal: Homo sapiens.
Of course, evolution doesn’t work like that, as Darwin had made clear. It has no goal, it is not regular, it leaves many species by the wayside, and it does not always lead to greater complexity. Evolutionary biologist and historian of science Stephen Jay Gould denounced the image in his 1989 book “Wonderful Life,” protesting that life is “not a ladder of predictable progress.”
So why has this misleading image prevailed? Even though it fails as science, it has been hugely successful as a lightning rod for debate. A look at the multiple ways this image has been used over time—as a joke, as commentary, as scientific fact—offers a glimpse of what historian Janet Browne suggests are “common anxieties about the implications of evolutionary ideas.” What it represents is a society struggling not just over how to understand—or indeed whether to accept—evolution, but also over a host of other divisive issues, from who is qualified to speak about science to what it means to be human.
Frontispiece of Thomas H. Huxley’s “Evidence as to Man’s Place in Nature”(1863), drawn by Benjamin Waterhouse Hawkins and engraved by William Henry Wesley. Eight years before Darwin addressed hominid evolution in “Descent of Man,” Huxley published this sequence of skeletons progressing toward ever-higher stages of development, a more palatable image than Darwin’s picture of deadly competition and random development. As historian Constance Clark has pointed out, “the proximity of the human figure to the apes, along with the left-to-right direction from apes to humans, would evoke familiar echoes of the old notion of a linear chain of being.”
Edward Linley Sambourne,“Man is But a Worm,” Punch’s Almanack for 1882 (Dec. 6, 1881). This wood engraving appeared in the satirical magazine Punch shortly after the publication of Darwin’s last book, “Worms.” In a depiction of evolution that ridicules any link between humans and primitive species, the sequence starts at the bottom left with “chaos” and an earthworm, then continues through spermatozoid creatures to apes, cavemen, a top-hatted Victorian dandy, and finally Darwin, whose pose tauntingly recalls Michelangelo’s depiction of Adam in the Sistine Chapel.
“The Rise and Fall of Man,” The New Yorker (1925). The ape-to-man image had become the dominant depiction of evolution by the 1920s, according to Clark. This pro-evolution cartoon, published during the Scopes trial, the American legal test of Tennessee’s law against teaching evolution in public schools, depicts a progression and then a backslide, according to the mocking caption: the final image shows William Jennings Bryan, the lawyer defending the anti-evolutionist position.
Rudolph Franz Zallinger, “The Road to Homo Sapiens,” in F. Clark Howell’s “Early Man” (Time-Life Books, 1965): When this fold-out picture depicting “man’s long march from apelike ancestors to Homo sapiens” appeared, it caused an immediate sensation. Today it remains one of the most famous scientific illustrations ever produced. As paleoanthropologists discovered new skeletal parts—indicated by white highlights—they were being fitted not into a branching Darwinian scheme, but into the framework of the original Huxley diagram. Although the text clarified that the evolution of man could not be reduced to a linear sequence, it was read that way by many viewers. The author later reflected, “The graphic overwhelmed the text. It was so powerful and emotional.”
“Evolution of Flavor,” Dr Pepper Facebook ad, 2012. Dr Pepper’s riff on the drawing arrives at a moment when the debate over evolution is more polarized than ever, at least in the United States: A May Gallup poll showed that 46 percent of Americans believe God created humans in a single act in the last 10,000 years, whereas “only a small number of nineteenth-century creationist writers” in the Victorian era believed this, as historian Ronald Numbers has written. Creationists denounced the company, but they’re fighting an uphill battle: Today, the image is ubiquitous in popular culture. It appears in cartoons, T-shirts, bumper stickers, social networking sites, and even campaign propaganda—in short, everywhere the idea of progress is sold.Jennifer Tucker is an associate professor of history, science in society, and gender studies at Wesleyan University, and the author of
“Nature Exposed: Photography as Eyewitness in Victorian Science” (Johns Hopkins, 2006).