It has long been presumed that primate societies were predominantly run by males. With the exception of lemur society, which was thought to be an outlier, most , including gorillas, chimps, and monkeys were believed to be largely male-dominated. Now, a literature review of 79 primate species is challenging that long-held assumption, suggesting that things are a lot more equal than they seem.
Researchers at The University of Texas have suggested that although male power dynamics are more common, female-biased power structures, or even social equality between males and females of a primate social group, can be found in every major living primate clade and likely even existed throughout their evolution.
“In the past, primatologists have often focused on the role of males and male power in primate societies,” said Rebecca Lewis, a professor of anthropology and co-author of the paper, in a . “What has sometimes been overlooked is the important role of female power in primate societies.”
The team divided the 79 primate species into groups based on whether they were female-dominant, male-dominant, or co-dominant, and which factors were common across these groups. For instance, the team found that female dominance was more likely to be the case in social groups when the size difference between males and females was smaller.
The study also took into account the challenges with categorizing species in this way and the authors write in the paper that the female and co-dominant groups “exhibit very different intersexual social relationships than species labeled as male dominant.”
Overall, the team found that 58 percent of the species that they looked at did exhibit male-biased power in their social groups. However, in Old World monkeys and apes, the team found multiple examples of species that do not have a male power style social dynamic. New World monkeys had the most variable power structures, with 40 percent of those species either co- or female-dominant.
While lemur society has been known to be female-led, other smaller primate species such as gibbons and were also likely to show female or co-dominant power structures. The team found that male-biased power was associated not only with males being larger than females, but also when there were more females within a group.
“Our work suggests that more economic forms of power might really come to the forefront in primate species in which males and females are similar in size and in which females are therefore less readily coerced by males,” continued Lewis.
Looking not just at modern primates, but back into the , the researchers also think that the assumption that most primate groups were male-dominated through evolutionary time is not accurate. They suggest that the last common ancestor of primates did not necessarily live in a male-dominated society, but the last common ancestor of monkeys, apes, and most likely did.
“Primates have been thought to be mainly male dominant, which would suggest that male dominance was present in primates from early in their evolutionary history,” said Chris Kirk, a professor of anthropology at UT and a co-author. “However, we show that this assumption of ancestral male-biased power in primates isn’t necessarily supported by the data.”
The study is published in