Charles Darwin had a problem with human faces. Not his own, though his enormous beard certainly obscured most of it by the 1870s. The problem was scientific. Darwin believed that human emotions – fear, joy, anger, disgust, surprise – were not uniquely human. He believed they were inherited from our animal ancestors, shaped by natural selection, and expressed through muscles and movements that we share with other species. He needed to prove it.
Words alone would not do. You can describe a snarl all you like, but until you see a snarling dog next to a sneering human, the comparison lacks force. Darwin needed pictures. And in 1872, he published what may be the most visually audacious scientific book of the nineteenth century: The Expression of the Emotions in Man and Animals.
It was one of the first scientific works to use photographs as evidence. It sold 5,267 copies on its first day. And it laid the foundation for an entire field of research that would not fully come into its own for another hundred years.
Why Darwin Wrote It
The book grew out of a chapter that got too long. While writing The Descent of Man (1871), Darwin found that his notes on emotional expression kept expanding. He had been collecting observations for over thirty years – since the voyage of the Beagle, since watching his own children as infants, since exchanging letters with missionaries, zookeepers, and asylum superintendents around the world.
Darwin had a specific argument to make, and it was controversial. The prevailing view, championed by the anatomist Sir Charles Bell, held that human facial muscles were specially designed by God to express the soul’s inner states. Expressions were a divine gift, unique to humans, and they had no evolutionary explanation.
Darwin disagreed completely. He proposed three principles to explain why we express emotions the way we do:
- Serviceable associated habits: expressions that originally served a practical function (baring teeth to bite, for instance) became habitual and persisted even when the function was no longer needed
- Antithesis: opposite emotions produce opposite physical postures (think of a dog cowering versus a dog bristling with aggression)
- Direct action of the nervous system: some expressions result simply from the overflow of nervous energy, with no adaptive history
These principles implied that emotions were biological, not spiritual. They were evolved responses, shared across species, and readable through the body. To prove this, Darwin needed evidence that was visceral, immediate, and hard to argue with. He needed photographs.
The Photographs
Darwin used several sources of imagery. The most striking were the photographs by Oscar Rejlander, a Swedish-born photographer working in London who was already known for his artistic and somewhat theatrical compositions. Rejlander posed himself and others to illustrate specific emotions: disgust, surprise, contempt, helplessness. The results were sometimes exaggerated, sometimes eerily natural.
Darwin also used photographs by Guillaume-Benjamin-Amand Duchenne de Boulogne, a French neurologist who had conducted extraordinary (and, by modern standards, unsettling) experiments in the 1850s and 1860s. Duchenne used electrical stimulation to activate individual facial muscles in his subjects, producing expressions that were anatomically precise but eerily artificial. His photographs showed exactly which muscles produced a smile, a frown, or a look of terror.
The combination was powerful. Where Duchenne provided the anatomy, Rejlander provided the life. Together, they gave Darwin a visual vocabulary for emotions that no previous scientist had possessed.
The Heliotype Process
Including photographs in a book was not a simple matter in 1872. The standard method for reproducing images in print was engraving – a skilled craftsman would hand-cut a metal plate based on the original image. This worked well for drawings and diagrams but destroyed the tonal subtlety of photographs.
Darwin’s publisher, John Murray, used a relatively new technique called the heliotype (a form of collotype printing). This process could reproduce the continuous tones of a photograph without reducing it to lines and dots. The results were impressive – the plates in The Expression of the Emotions have a photographic quality that looks remarkably modern, even today.
It was also expensive. The heliotype plates had to be printed separately and tipped into the book by hand. This added significantly to the production cost. But Darwin and Murray believed – correctly – that the visual impact was worth it. The photographs made the book’s arguments far more compelling than text alone ever could.
The Evidence from Everywhere
Darwin did not rely solely on photographs. His research methods were astonishingly broad for the period. He sent printed questionnaires to contacts around the world – missionaries in Africa, colonists in Australia, traders in India – asking them to observe the facial expressions of indigenous peoples. Do they blush? Do they frown when puzzled? Do they shrug their shoulders?
The responses were inconsistent and sometimes colored by the observers’ prejudices. But the overall pattern supported Darwin’s thesis: the same basic expressions appeared across cultures that had no contact with one another. Surprise looked like surprise in London and in Tierra del Fuego. Grief looked like grief in India and in the Australian bush.
Darwin also drew on observations of:
- Infants, whose expressions could not have been culturally learned (he had meticulously documented his own children’s facial movements from birth)
- The blind, who produce recognizable facial expressions despite never having seen them in others
- Animals, particularly dogs, cats, and primates, whose emotional expressions bore clear structural similarities to human ones
- Patients in psychiatric institutions, whose extreme emotional states made certain expressions more visible and easier to study
The breadth of this evidence was remarkable. Darwin was doing something that would not have a name for decades: cross-cultural psychology. He was using comparative methods across species, across cultures, and across developmental stages to build a biological case for the universality of emotional expression.
The Book’s Reception and Long Afterlife
The book sold remarkably well. The first print run of 7,000 copies was almost entirely spoken for before publication day. Reviews were mixed – some critics found the photographs grotesque, others found the theoretical framework unconvincing – but the public loved it. It was Darwin at his most accessible, writing about something everyone could relate to: feelings.
Then, for nearly a century, the book was largely forgotten by the scientific mainstream. Psychology moved on to behaviorism, which dismissed internal states like emotions as unscientific. Anthropologists emphasized cultural relativism and were skeptical of claims about universal human nature. Darwin’s Expression gathered dust.
The revival came in the 1960s and 1970s, when the psychologist Paul Ekman began conducting cross-cultural studies of facial expressions. Working with isolated communities in Papua New Guinea, Ekman found strong evidence for a set of basic emotions – happiness, sadness, fear, anger, surprise, disgust – that were recognized across all cultures. His research directly validated Darwin’s central claims, and Ekman was explicit about the debt. He later edited an annotated edition of The Expression of the Emotions, calling it “still the single most important work on the subject.”
A Book Made for Our Visual Age
There is an irony in the history of The Expression of the Emotions. It was Darwin’s most visual book, published in an era when visual reproduction was expensive and difficult. Today, in a world saturated with images – where we communicate emotions through emoji, GIFs, and video – Darwin’s approach feels strikingly modern. He understood intuitively what social media has confirmed: when it comes to emotions, showing is more powerful than telling.
The engravings and photographs in Expression are part of a much larger visual legacy scattered across Darwin’s published works. From the single branching diagram in On the Origin of Species to the detailed botanical plates in his later books, Darwin consistently used images to make invisible processes visible. This tradition of scientific visualization – of making evidence something you can see and feel – is explored beautifully in Portraying Science, and it connects Darwin to a broader history of researchers who understood that the eye can be as persuasive as the argument.
For those drawn to the intersection of art and natural history, Humboldt’s visual explorations of nature offer another stunning example of how scientists have used images not merely to illustrate their findings, but to embody them.
Darwin’s faces – human, animal, photographed, engraved – stare out from the pages of a 150-year-old book and ask a question we are still answering: are our deepest feelings our own, or do they belong to a much older story? The evidence, as Darwin would say, is written on our faces.
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