New Clues to the Origins of Human Medicine: Chimpanzees Caught Healing Each Other’s Wounds in the Wild

Scientists observed chimpanzees in Uganda appearing to clean and treat both their own wounds and those of others.

Scientists studying chimpanzees in the Budongo Forest of Uganda have found that these primates not only treat their own injuries but also care for the wounds of others. This behavior may offer insight into how early humans began treating injuries and using medicinal practices. While similar actions have been observed in other chimpanzee communities, the consistent occurrence of this behavior in Budongo suggests that medical care among chimpanzees may be more common and not limited to helping close relatives.

“Our research helps illuminate the evolutionary roots of human medicine and healthcare systems,” said Dr. Elodie Freymann of the University of Oxford, first author of the article in Frontiers in Ecology and Evolution. “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 healthcare behaviors.”

Community care

The scientists studied two chimpanzee communities in the Budongo Forest: Sonso and Waibira. Like all chimpanzees, individuals in these groups are susceptible to injuries from fights, accidents, or human-made snares. In the Sonso community, about 40% of the chimpanzees have been observed with snare-related injuries.

Researchers observed each community over a four-month period and also reviewed video footage from the Great Ape Dictionary database, long-term logbooks with decades of observational data, and surveys from other scientists who had witnessed chimpanzees treating injuries or illness. They identified the plants used by chimpanzees for external treatment, and several were found to have chemical properties associated with wound healing and traditional medicinal use.

A young chimpanzee cares for a wound on his left knee with chewed stem bark and fresh leaves, filmed by Dr. Elodie Freymann. Credit: Dr. Elodie Freymann

During their direct observational periods, the scientists recorded 12 injuries in Sonso, all of which were likely caused by within-group conflicts. In Waibira, five chimpanzees were injured — one female by a snare, and four males in fights. The researchers also identified more cases of care in Sonso than in Waibira.

“This likely stems from several factors, including possible differences in social hierarchy stability or greater observation opportunities in the more thoroughly habituated Sonso community,” said Freymann.

The roots of modern medicine?

The researchers documented 41 cases of care overall: seven cases of care for others — prosocial care — and 34 cases of self-care. These cases often included several different care behaviors, which might be treating different aspects of a wound, or might reflect a chimpanzee’s personal preferences.

“Chimpanzee wound care encompasses several techniques: direct wound licking, which removes debris and potentially applies antimicrobial compounds in saliva; finger licking followed by wound pressing; leaf-dabbing; and chewing plant materials and applying them directly to wounds,” said Freymann. “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.

“We also documented hygiene behaviors, including the cleaning of genitals with leaves after mating and wiping the anus with leaves after defecation — practices that may help prevent infections.”

Who cares?

Of the seven instances of prosocial care, the researchers found four cases of wound treatment, two cases of snare removal assistance, and one case where a chimpanzee helped another with hygiene. Care wasn’t preferentially given by, or provided to, one sex or age group. On four occasions, care was 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.

The scientists call for more research into the social and ecological contexts in which care takes place, and which individuals give and receive care. One possibility is that the high risk of injury and death which Budongo chimpanzees all face from snares could increase the likelihood that these chimpanzees care for each other’s wounds, but we need more data to explore this.

“Our study has a few methodological limitations,” cautioned Freymann. “The difference in habituation between the Sonso and Waibira communities creates an observation bias, particularly for rare behaviors like prosocial healthcare. While we documented plants used in healthcare contexts, further pharmacological analyses are needed to confirm their specific medicinal properties and efficacy. Also, the relative rarity of prosocial healthcare makes it challenging to identify patterns regarding when and why such care is provided or withheld. These limitations highlight directions for future research in this emerging field.”

Reference: “Self-directed and prosocial wound care, snare removal, and hygiene behaviors amongst the Budongo chimpanzees” by Elodie Freymann, Catherine Hobaiter, Michael Alan Huffman, Harmonie Klein, Geresomu Muhumuza, Vernon Reynolds, Nora E. Slania, Adrian Soldati, Eguma Robert Yikii, Klaus Zuberbühler and Susana Carvalho, 26 March 2025, Frontiers in Ecology and Evolution.
DOI: 10.3389/fevo.2025.1540922

Funding: Clarendon Fund, Keble College, Horizon 2020 Framework Programme, University of Algarve

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