Researchers have documented surprising behavior among chimpanzees in the Budongo Forest in Uganda: not only do they treat their own wounds, but they also help other members of their group—even when there is no genetic relationship and despite the risk of being exposed to pathogens. The finding, published in Frontiers in Ecology and Evolution, could shed light on the evolutionary roots of human medicine and healthcare systems, according to lead author Elodie Freymann of the University of Oxford.

The study focused on two chimpanzee communities, Sonso and Waibira, over four months of direct observation, along with the analysis of decades of video records and field notebooks. Scientists identified 41 instances of medical care, including both self-treatment and aid to others.

Among these, seven episodes of prosocial care stand out, in which individuals applied chewed leaves from plants with known medicinal properties to the wounds of their companions, removed traps, and even assisted in hygienic practices.

Healing Techniques and Medicinal Plants

The chimpanzees used multiple methods to treat injuries, from directly licking wounds—which might help remove debris and apply antimicrobial compounds present in saliva—to applying fresh leaves or chewed stems. Some of the plants used and identified by researchers have documented uses in traditional medicine and bioactive properties that promote healing.

Chimpanzees heal each other
[Top left] KO chews stem bark of A. macrophylla. [Top right] KO detaches leaves from stem and dabs on wounded knee. [Bottom left] KO applies chewed stem bark to wound. [Bottom right] KO leaf-dabs with attached leaves. Credit: Elodie Freymann et al. / Frontiers

Wound care among chimpanzees includes a variety of techniques: pressing with previously licked fingers, rubbing with leaves, and the direct application of processed plant material, Freymann explained. All observed individuals recovered from their injuries, although we cannot be certain this was exclusively due to their interventions.

In addition to wound treatment, scientists recorded other hygienic behaviors such as cleaning the genitals with leaves after mating or the anus after defecation, which reduce the risk of infections.

Interestingly, the chimpanzees did not limit their help to close relatives. In four of the seven cases of prosocial care, individuals assisted companions with no direct genetic relationship, challenging the idea that altruism in animals is limited to immediate evolutionary benefits.

These behaviors strengthen the evidence that chimpanzees recognize the suffering of others and act to relieve it, even without a clear reproductive advantage, Freymann noted. Among the documented episodes are the removal of a metal snare from a female’s leg and the application of medicinal leaves to the wounds of adult males after intracommunity fights.

The frequency of these behaviors varied between the two communities studied. In Sonso, where 40% of individuals were affected by wounds from human traps, more cases of medical care were documented than in Waibira. This difference could be due to greater habituation of the Sonso chimpanzees to human presence, which facilitates observation by researchers, or to instabilities in Waibira’s social hierarchy that limit cooperative interactions.

Freymann also warns about the study’s limitations: Waibira’s low level of habituation generates an observational bias, especially in rare behaviors like prosocial medical care. Furthermore, more in-depth pharmacological analyses are needed to confirm the healing properties of the plants used.

The discovery that chimpanzees practice rudimentary forms of community medicine reinforces the hypothesis that human healthcare systems have deep roots in our evolutionary past. The ability to identify medicinal plants, combined with a willingness to help others—even at the risk of exposure to pathogens—suggests that empathy and medical cooperation are not exclusive to our species.

This research sheds light on how our ancestors may have begun treating injuries and illnesses, Freymann concluded. By studying chimpanzees, we see a reflection of behaviors that, over time, became the foundation of modern medicine.

SOURCES

Frontiers

Elodie Freymann et al., Self-Directed and Prosocial Wound Care, Snare Removal, and Hygiene Behaviors Amongst the Budongo Chimpanzees, Frontiers in Ecology and Evolution (2025). DOI: 10.3389/fevo.2025.1540922

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