It turns out baboon social life isn’t just about grooming and hanging around and may be more akin to high school than once thought, according to a new study co-authored by University of Massachusetts Amherst anthropologists.

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The research, published in the Proceedings of the National Academy of Sciences, found that baboons and their close relatives fall into three distinct social styles: the tight-knit crowd, the cliquey crowd and the “it’s complicated” crowd organized around powerful males.

The research, by a team that includes co-principal investigator Jason Kamilar, professor of anthropology at UMass Amherst, and Anna H. Weyher, who earned a doctorate in anthropology from UMass Amherst in 2023, is based on decades of field data spanning 11 species and 135 group-years, making it one of the most comprehensive looks yet at how primate societies actually work.

“Our work demonstrates the evolutionary flexibility of behavioral traits and primate social organizations,” Kamilar explains. “The grooming patterns and social cohesiveness of these species have both diverged from each other and independently evolved the same characteristics multiple times within a relatively brief evolutionary timespan.”

The study breaks baboon social life into three categories:

• Cohesive societies — Groups that are tightly connected, with strong kin-based relationships and moderate influence of dominance rank.
• Cliquish societies — Groups that form tighter subgroups, with stronger kinship and rank effects and more selective social ties.
• Multilevel societies — Highly structured systems where females cluster around dominant males, forming distinct social circles.

Researchers found that while kinship and social rank influence behavior across all groups, their strength varies significantly depending on the type of society. One feature that stands out is the unique role of males in multilevel societies. In these systems, females tend to form strong social bonds within clusters centered on dominant males, a pattern largely absent in single-level groups.

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The findings come from the Comparative Analysis of Papionin Societies (CAPS), a large collaborative database combining long-term observations from across Africa. Researchers focused on grooming—a key social behavior in primates—to map relationships and identify patterns in how groups cluster and interact.

By analyzing these networks, scientists were able to quantify how social relationships form and cluster within groups, revealing patterns that had previously gone undetected.

The findings offer fresh insight into the evolutionary forces shaping social systems in primates, including humans. The study suggests that differences in female kinship ties, competition and male influence may drive the emergence of distinct social structures.

“We are currently examining the environmental factors that play a role in driving behavioral and social system variation across these species,” Kamilar notes.

This research was supported by a Postdoctoral Fellowship from the U.S. National Science Foundation. Jacob Feder and Joan Silk, both of Arizona State University, served as principal investigator and co-PI, respectively.