The physical act of crying in humans is a complex, two-part response: the production of tears (lacrimation) and accompanying vocalizations and facial expressions. This response is triggered by intense emotional states and serves as a powerful social signal. Since chimpanzees share a close evolutionary relationship with humans, many inquire whether they also cry. Exploring the scientific answer requires separating the functional components of human crying to see which ones are present in our closest living relatives.
The Literal Answer: Tears and Lacrimation
Chimpanzees do not shed emotional tears in the same way humans do. While they experience strong emotions, the neurological connection linking these feelings to a flow of tears is absent in non-human primates. Emotional lacrimation—the production of tears in response to internal feelings like sadness or grief—is considered unique to the human species.
Chimpanzees, like other mammals, possess tear ducts and glands that produce tears for biological maintenance. These are known as basal or reflexive tears, which are necessary to lubricate the eye, clear debris, and protect the cornea from irritants. If a chimpanzee were to get sand in its eye or suffer a wound, reflexive tears would be produced. However, these tears do not stream down the face as a signal of internal distress.
Chimpanzee Distress Signals and Vocalizations
Since chimpanzees do not use tears to communicate distress, they rely on a sophisticated system of auditory and visual signals. When experiencing acute sadness, pain, or fear, their primary method of communication is vocalization. These sounds range from soft whimpers and whines in young individuals to loud screams and wails in intense situations.
A key distress signal is the loud, rhythmic vocalization known as a “pant-hoot,” which varies in intensity and pitch to convey urgency over long distances. When frightened or distressed, a chimp may also emit a “wraaaa” call, a long, loud sound that alerts others to danger. These auditory signals are often accompanied by distinct body language and facial expressions.
Visual signals of distress include the “pout,” a facial expression where the lips are protruded and compressed, and the “fear grimace,” characterized by a wide-open mouth and bared teeth. In moments of need, a young chimpanzee might engage in clinging behavior, seeking physical contact and comfort from its mother or another group member. These combined actions serve the functional equivalent of human crying, soliciting attention and help from their social group.
Evolutionary Roots of Human Emotional Crying
The divergence between human and chimpanzee responses to distress suggests that emotional weeping evolved after the two species separated. Emotional crying is widely hypothesized to have developed in humans as an important social signal. Unlike the loud, attention-drawing calls of a distressed chimpanzee, a human’s silent tears serve as a visually clear, non-threatening signal of vulnerability and need.
One prominent theory suggests emotional tears evolved to signal distress without attracting predators in early hominid environments. A loud scream draws danger, but a tearful face is a silent, visual plea encouraging prosocial behaviors like empathy and support. Studies suggest that seeing a person cry makes them appear more friendly and less aggressive, promoting social bonding.
Emotional tears also have a different chemical composition than reflexive tears, containing higher concentrations of stress hormones. This has led some to propose that crying serves a self-soothing function. By releasing these hormones and stimulating the production of endogenous opioids, crying may help regulate an individual’s emotional state. This complex system of visual signaling and internal regulation cemented emotional weeping as a unique characteristic of human behavior.