Most students encounter Charles Darwin — the man behind the Origin of Species — at some point in their academic career, whether it be during high school, a mandatory introductory biology class or an upper level evolution course. This week, the Mann Library lobby exhibit “Written on our Faces” will be honoring one of Darwin’s lesser known works, The Expression of the Emotions in Man and Animals.

Darwin, an 19th century English naturalist, has become a household name in the field of evolutionary biology for writing the books that are considered to be the foundation of the field. The basis of Darwin’s argument for evolution by natural selection was founded on observations of physical similarities and differences between closely related species, a study now known as homology. However, Darwin further bolstered his argument by juxtaposing the facial expression of emotion between humans and their close relatives, which he published in The Expression of Emotion in Man and Animals.

Studies have found that human facial structure results in the most telling facial expressions of any species. The presence of eyebrows, more visible white in the eyes, more pronounced lips and additional muscles in the faces has expanded the repertoire of expressions humans can make to articulate more complex emotions, such as love and disappointment. On the other hand, other species can only communicate simple emotions and often must use other body parts to fully express themselves. Therefore, the use of emotional expression was crucial to the development of the more complex communication that is characteristic of Homo sapiens.

“Darwin really hoped to prove two things. One is that expressions are largely universal and, therefore, probably have more of a physical and genetic basis rather than a cultural basis,” Liz Brown, the curator of the exhibit, explained. “The other is that we share facial expressions with non human species and the reason that he wanted to prove that was so it would lend strength to his argument that in fact human beings share genetic history with other species.”

As Darwin observed, all humans, regardless of race, use the same muscle contractions and facial movements for simple and complex emotions. These observations lent themselves to the theory that individuals who were better able to communicate through expression were more likely to reproduce and pass on their genes.

Darwin further explored the facial expressions of primates and other mammals to prove the evolutionary connections between the species. Most notable are the similarities between humans and primates. Even before the Jane Goodall’s studies involving the social habits of chimpanzees, Darwin and other scientists such as Nadezha Ladygina-Kohts had observed the similarities between the expression of simple emotions in human and chimpanzee infants. It is now known through more in-depth evolutionary analysis that chimpanzees are the most closely related species to humans.

“Darwin wanted to indicate that the universality of facial expressions was just one more indication that all human beings are related to one another and the fact that we share facial expressions with primates, indicates that we are related to primates.” Brown elaborated.

The impact of The Expression of the Emotions in Man and Humans went further than merely supporting the theory of evolution by natural selection. In his book, Darwin sparked interests in new fields of study. “Expression was seminal in several different disciplines. He was really one of the first ethologists, so many people who study ethology or primate anthropology site this book as their genesis. There’s also now an entire field in psychology studying facial expressions.” Brown said. Ethology is the scientific study of animal behavior.

The exhibit will be on display in the Mann Library lobby until Sept. 15. The exhibit will display pieces from Mann Library’s Rice Poultry Collection, which honors James E. Rice, the first professor in poultry husbandry and houses some of the earliest works in poultry husbandry.