Humans are hardly the only animals who can discern the nuances of rank and familial status. According to findings from Robert Seyfarth, chairman of the Department of Psychology, and Dorothy Cheney, professor of biology, baboons recognize each other through an intricate system of relationships that reflect rank and hierarchy between and within families. These findings were reported in the Nov. 14 issue of the journal Science.

Cheney and Seyfarth have unraveled a matrilineal system where the primates recognize each other’s dominance and respond to playbacks of calls and grunts that simulate fights between baboons that run in different social circles. Cheney compared the matrilines to the intricacies in a Jane Austen novel. “They live in groups that are ostensibly very complex,” she said. Baboons have multiple social relationships, and appear to recognize their kin and allies of themselves and others. Cheney and Seyfarth are also exploring how these social relationships may have influenced similar ones in humans and contributed to the development of intelligence and language.

Seyfarth and Cheney have been working with primates for more than 20 years, and have worked with colleagues since 1992 to study more than 80 baboons that live in the Moremi Game Reserve, located in the Okavango Delta in the northwest part of Botswana. In that time, they have documented and tested relationships that exist between 25 females in the matrilineal society. Baboons have matrilines where female members of one family are outranked by or outrank other families; female baboons are also ranked within their own families.

Cheney and Seyfarth’s results demonstrate that baboons organize themselves into a hierarchical structure, but the question remains if in their minds, baboons organize their social and familial relationships into a similarly complex pattern. “These animals don’t have words for family. They do have the knowledge about the familial relationship,” said Seyfarth. “They seem to organize this information in their brain.”

Researchers used audio playbacks of distinct grunts—the cries of dominant baboons—and screams—the calls of lower-ranking ones—to simulate fights between and within families. Through video analysis, the team discovered that baboons pause if they hear a fight between family members but responded more strongly to fights between two entire families. A between-family conflict would carry more potential for rank change than one between individual family members.

Seyfarth and Cheney will travel back to the remote reserve this summer to join their postdoctoral fellows and continue their present research studying stress hormone secretion in female baboons. Cheney said that through analysis of fecal samples which contain stress hormones, they have found that social stresses such as pregnancy and lactation—times when males can be very aggressive—cause female baboons more stress than the presence of lions.