Baboons are usually defined by rigid hierarchies and tense male-female relationships. In most species, adult males live on the periphery of groups, engaging with females primarily for mating. Dominance is enforced through aggression, and competition can be fierce—rivalries often lead to violent confrontations, and in some cases, infanticide.
But in the forests of Zambia’s Kasanka National Park, Kinda baboons (Papio kindae) are doing something different. A new study, led by anthropologist Anna Weyher and published in the American Journal of Biological Anthropology1, suggests that among Kindas, males and females maintain unusually close social bonds. Rather than merely seeking mating opportunities, male Kindas appear to invest in long-term relationships with females, spending more time grooming and interacting with them than their counterparts in other baboon species.
According to Weyher, this behavior is striking:
"Kinda males are initiating these relationships. They’re spending more time maintaining them, they’re grooming females in all reproductive states."
This level of social connection challenges what researchers thought they knew about baboon mating systems—and may offer insights into how social bonds evolved in primates, including humans.
Less Fighting, More Friendship
In most baboon societies, males reach sexual maturity and leave the group they were born into, joining a new one where they must fight their way up the hierarchy. The reward for dominance is access to mating, but the strategy is costly. High-ranking males must constantly defend their status, often resorting to aggression. Infanticide—where males kill the offspring of rivals—is another brutal but common way dominant males ensure their genes are passed on.
Kinda baboons, however, don’t seem to follow this pattern. Weyher and her team found that males invest less energy in physical aggression and more in social bonding. This cooperative approach may be influenced by their unique physical characteristics.
Unlike other baboon species, Kindas are smaller, and the size difference between males and females—known as sexual dimorphism—is minimal. This is a major departure from the standard baboon model, where males can be nearly twice the size of females.
Anthropologist Jason Kamilar, a co-author of the study, points out that this reduced size difference makes Kindas particularly interesting for researchers studying social evolution in primates:
“Kindas are the least sexually dimorphic baboon species, so they may offer the best model for understanding human social behavior.”
Another theory behind the Kinda’s social strategy comes down to reproduction itself. In most primates, large-bodied males tend to rely on physical dominance to secure mating opportunities. But Kinda males appear to employ a different tactic—sperm competition.
"If you control for body size, Kinda males have the biggest testicles," Weyher notes.
This suggests that instead of relying on brute force to monopolize females, Kinda males may be using a more subtle strategy: forming strong bonds that give them preferential access to mates over time.
A Model for Human Social Evolution?
For scientists studying primate social structures, Kindas offer an intriguing possibility—an alternative pathway to reproductive success that relies on cooperation rather than competition. While dominance hierarchies and aggression define many primate societies, Kindas suggest that social bonding can also be an effective evolutionary strategy.
"In some ways, it’s not surprising that Kindas behave so differently," Kamilar explains. "Anatomically, they already look very different from other baboons."
Their unique approach to male-female relationships has even drawn comparisons to human social behavior. Public radio’s Science Friday jokingly framed Weyher’s research in the context of When Harry Met Sally—asking whether male and female baboons can really be “just friends.”
The answer, at least for Kindas, appears to be yes. But it may also be more than that. Strong, long-term social bonds could have benefits beyond friendship, giving males an advantage when mating season arrives.
The Kasanka Baboon Project and the Future of Kinda Research
Weyher’s study is part of the Kasanka Baboon Project, a long-term research initiative she founded in 2010. In addition to studying Kindas, the project promotes conservation efforts and education in local Zambian communities.
Research into Kinda baboons is still in its early stages, but their unusual social behavior is already raising important questions about the evolution of cooperation and bonding in primates. If these small, unassuming baboons can succeed without the constant violence seen in other species, perhaps their society holds lessons about how early humans developed our own complex social structures.
Weyher, A. H., Katinta, M., Mubemba, B., Petersdorf, M., Kamilar, J. M., Schneider-Crease, I. A., & Chiou, K. L. (2025). A friendlier “Kinda” social system: Male Kinda baboons invest in long-term social bonds with females. American Journal of Biological Anthropology, 186(1), e25056. https://doi.org/10.1002/ajpa.25056
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