Chimpanzees in Uganda’s Budongo Forest have been seen applying medicinal plants not just to heal their own wounds but also to care for the wounds of other group members. This extraordinary behavior, similar to primitive first aid, illuminates the ancient roots of health care and healing among human ancestors, a new study in Frontiers in Ecology and Evolution reports.
While isolated instances of chimpanzees helping others with injuries have been seen before, the sustained presence of such behaviors across two communities in Budongo suggests these practices may be far more widespread and socially embedded than previously believed. The researchers say the findings mark a crucial step toward understanding how and why early hominins might have begun treating injuries and each other, with medicinal remedies.
Chimpanzees as Caregivers
“Our research helps illuminate the evolutionary roots of human medicine and health care systems,” said Dr. Elodie Freymann, the study’s first author and a biological anthropologist at the University of Oxford. “By documenting how chimpanzees identify and utilize medicinal plants and provide care to others, we gain insight into the cognitive and social foundations of human health care behaviors.”
Freymann and her colleagues observed two chimpanzee groups, the Sonso and Waibira communities, living in the Budongo Forest Reserve in western Uganda. The research team conducted four months of focused observation of both groups, supplemented with decades of logbook entries, archived videos from the Great Ape Dictionary project, and expert surveys of other field scientists.
Both communities are familiar to researchers, with Sonso being more thoroughly habituated to human presence than Waibira. This made close observation easier in Sonso, and may partially explain why more examples of caregiving were observed there.
A Dangerous Life in the Forest
Chimpanzees in Budongo face numerous hazards, ranging from intra-group fighting to the cruel legacy of human snares, wire traps set by poachers that often leave primates maimed or worse. According to Freymann, roughly 40% of individuals in the Sonso group have visible snare injuries. These threats create an environment where health-related behaviors may become essential for survival.
Throughout the study, researchers documented 12 injuries among Sonso chimpanzees, primarily resulting from in-group conflicts. In Waibira, five individuals sustained wounds, one female from a snare, and four males from fights. Despite the difference in sample size, researchers identified several instances of active care.
In total, 41 distinct episodes of medical behavior were recorded, divided into 34 cases of self-care and seven acts of prosocial care, where one chimpanzee helped another.
Primitive First Aid, Chimpanzee Style
The researchers observed chimpanzees using multiple techniques to tend to wounds. These included licking injuries directly, possibly using antimicrobial compounds in their saliva, or licking their fingers and then pressing them to wounds. Some were seen applying leaves to the affected areas, either by dabbing or chewing the plant material before placing it on the skin.
The scientists took special care to identify the plant species used, many of which have known medicinal properties in traditional medicine or chemical traits that promote healing, such as anti-inflammatory or antimicrobial effects.
“All chimpanzees mentioned in our tables showed recovery from wounds, though, of course, we don’t know what the outcome would have been had they not done anything about their injuries,” Freymann said.
Aside from first-aid treatment, the scientists also documented hygiene-related behaviors. These were cleaning genitals with leaves after copulation and wiping the anus with foliage after defecation, indicating a primitive awareness of infection prevention.
Helping Others, Even Without Personal Gain
Among the seven cases of prosocial care, four involved direct wound treatment, two focused on helping individuals remove snares, and one case involved hygiene assistance. Importantly, this care was not restricted by gender, age, or kinship. Four of the observed instances involved care given to genetically unrelated individuals.
“These behaviors add to the evidence from other sites that chimpanzees appear to recognize need or suffering in others and take deliberate action to alleviate it, even when there’s no direct genetic advantage,” said Freymann.
This tendency to offer help outside of family circles, and without expectation of immediate reward, is a vital piece of what distinguishes complex social species, and what links these primates to the evolutionary roots of human caregiving.
Community Dynamics May Play a Role
The Sonso community exhibited more instances of care than Waibira, though researchers caution against reading too much into this difference without further data.
“This likely stems from several factors, including possible differences in social hierarchy stability or greater observation opportunities in the more thoroughly habituated Sonso community,” Freymann explained.
In addition, chimpanzees in Budongo experience significant environmental pressure, especially the threat of snares, which may encourage a culture of caregiving as a form of social cohesion or survival strategy. The researchers suggest that such contextual factors might increase the likelihood of prosocial health behaviors becoming established and normalized.
Medicinal Plants and Human Parallels
The study not only documents care behaviors but also reinforces the idea that chimpanzees recognize certain plants for their healing properties, whether through instinct, learning, or observation. These findings may change the way scientists view the earliest history of pharmacological knowledge in our ancestors.
Some of the plants described in the study are employed in Ugandan traditional medicine, which opens the door to the possibility that chimpanzees and humans do have a shared pharmacological vocabulary driven by common environments and comparable health threats.
“By analyzing how these animals interact with their ecosystem in a healing context, we can trace the origins of some of our own medicinal practices,” Freymann said.
Challenges and the Road Ahead
Freymann acknowledges that the study has limitations. For one, the variability in habituation levels between Sonso and Waibira might introduce an observation bias, particularly for infrequent behaviors such as prosocial care. Moreover, although the group noted which plants were utilized, laboratory testing would be required to establish the exact medicinal properties and effectiveness of the plant species involved.
Another limitation is the frequency of some of the behaviors. With only seven recorded cases of prosocial care, it’s difficult to form definitive conclusions about patterns or motivations. That’s why Freymann and her colleagues are calling for more studies, especially those that explore the social and ecological conditions under which chimpanzees are more likely to offer care.
“The relative rarity of prosocial health care makes it challenging to identify patterns regarding when and why such care is provided or withheld,” Freymann noted. “These limitations highlight directions for future research in this emerging field.”
A Glimpse Into Our Past
Though limited in sample size, the new findings offer a fascinating window into the lives of our closest living relatives and, by extension, into the lives of our ancient ancestors.
From using plants with pharmacological benefits to helping others recover from injuries, the behaviors of Budongo’s chimpanzees reveal a complex interplay of cognition, empathy, and ecological knowledge that likely underpins the origins of medicine itself.
As scientists continue to observe and learn from these primates, we may come closer to answering some of the biggest questions about the birth of health care, the evolution of compassion, and what it truly means to care for one another.
