Baboons may offer clues to early human social evolution

Remarkable social behaviors have been discovered in Kinda baboons (Papio kindae) that set them apart from other baboon species. 

The research, led by University of Massachusetts Amherst anthropologist Anna Weyher, was conducted over nine years in Zambia’s Kasanka National Park.

The study reveals that male Kinda baboons form strong, long-term social bonds with females, a behavior uncommon in most baboon species.

Unlike their more aggressive and competitive relatives, Kinda males initiate and maintain affiliative relationships with multiple females, forming lasting friendships that persist beyond mating periods. 

These findings suggest that the social structures of Kinda baboons challenge traditional classifications of baboon behavior and could provide valuable insights into primate evolution, including early human social dynamics.

“In some ways, it’s not surprising that, behaviorally, Kindas are so different because, anatomically, they look a lot different than other baboons,” said Jason Kamilar, professor of anthropology at UMass Amherst and co-author of the study. 

“Kindas are the smallest baboons and they’re also the least sexually dimorphic, so the difference in body size between males and females is the smallest – making them the best baboon species [for us] to understand humans.”

Unusual male-female social bonds

In most baboon species, female social bonds dominate, and male-female relationships are typically short-lived, forming primarily around mating opportunities. However, Kinda baboon males take a different approach, prioritizing affiliative relationships with females.

Researchers found that male Kindas were the primary initiators of social interactions. They frequently engaged in proximity maintenance (staying close to specific females for extended periods), grooming (a key social behavior in primates that promotes trust and reduces stress), and long-term friendships lasting years, rather than being tied solely to reproduction.

These findings suggest that male-female bonds serve a broader social function beyond mating. The benefits for males could include increased reproductive opportunities, while females may gain social stability, reduced harassment, and greater protection.

Baboons and cooperative social dynamics

Another striking discovery was the notably low level of aggression among Kinda males. In most baboon species, males compete aggressively for dominance, engaging in frequent battles over access to mates.

However, the study found that Kinda baboons display minimal aggression toward each other and toward females.

“What we’ll typically see is that a male from outside the group will enter the study group, but they do so without much fanfare,” Kamilar explained. 

“The new male will have to slowly move his way up the social hierarchy. That’s very different from yellow baboons, for instance, where you’ll have an individual male come in as an alpha and basically take over the group.”

Instead of forcefully challenging dominant males, new male Kinda baboons integrate gradually, forming relationships with group members rather than disrupting existing social structures.

This “long-game” strategy contrasts sharply with other baboon species, where males frequently battle for alpha status. The researchers believe this unique approach could provide evolutionary advantages, promoting cooperative relationships rather than dominance-based competition.

Rethinking baboon social structures

The study’s findings challenge the traditional classification of baboon social models. Historically, baboons have been grouped into two primary social structures. 

The “savannah” model is characterized by strong female bonds, with males competing aggressively for mates, as seen in species like yellow and olive baboons. 

In contrast, the “hamadryas” model features rigid, male-dominated groups where males exert strong control over female movements, a structure typical of hamadryas baboons.

However, Kinda baboons don’t fit neatly into either category. Instead, they exhibit a blend of social behaviors, where males form lasting social ties with females without controlling them.

According to the experts, Kinda baboons exhibit a variety of behaviors, with male-driven social investment similar to that of hamadryas baboons, but within a more fluid and egalitarian group structure.

This raises intriguing questions about the evolution of social behavior in primates, suggesting that Kinda baboons might represent an ancestral social system – one that predates the more hierarchical structures seen in other baboon species today.

A window into early human evolution?

Because Kinda baboons are the least sexually dimorphic of all baboon species, meaning males and females are closer in size than in other baboon species, researchers believe they offer insights into early human social evolution.

“Understanding how different primate species interact socially gives us clues about the evolutionary pressures that shaped human behavior,” Kamilar said.

The findings suggest that early primates – potentially including human ancestors – may have exhibited similar cooperative, male-female social bonds rather than strict dominance-based hierarchies. This could provide a model for understanding how early humans balanced competition and cooperation in their social groups.

Further research is needed

The Kasanka Baboon Project, founded by lead researcher Anna Weyher, continues to study Kinda baboons to further investigate their unique social structures. 

The team hopes to answer additional questions, such as: Do male-female friendships affect offspring survival rates? How do Kindas resolve conflicts without aggressive dominance struggles? Could this social model be more widespread among other primate species?

“Kinda baboons challenge many of our assumptions about primate behavior,” Weyher said. “By studying them, we’re not just learning about baboons – we’re uncovering new perspectives on how complex social behaviors evolve.”

By shedding light on the cooperative social strategies of Kinda baboons, this study not only deepens our understanding of primate behavior but also offers a fascinating glimpse into the social lives of our early ancestors.

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