Goodbye to the myth of the alpha male in the war of the sexes

The alpha male who dominates the group, especially the female members, is more myth than reality. They don't always, or even often, rule. For a long time, it was assumed that the few primate species in which female dominance is the norm, such as ring-tailed lemurs or bonobos , represented an exception requiring a special explanation. This is not the case.

In most primate species, neither sex clearly dominates the other, according to a study conducted by a team from the University of Montpellier, the Max Planck Institute for Evolutionary Anthropology in Leipzig, and the German Primate Center in Göttingen.

Researchers collected detailed observations of male-female aggression in 253 populations of 121 primate species. Upon reviewing the data, they realized that, contrary to popular belief, fights between the sexes are surprisingly common. On average, nearly half of aggressive interactions in social groups involved a male and a female.

"The observation that in most populations a given individual is more likely to engage in a fight against an individual of the opposite sex than against the same sex highlights that battle of the sexes is common in other animals," says Dieter Lukas of the Max Planck Institute for Evolutionary Anthropology.

But what were the outcomes of these violent encounters? Males dominated females—winning more than 90 percent of fights—in only 25 of the 151 populations studied. In contrast, clear female dominance was observed in 16 populations, leaving the remaining 70 percent with moderate or no sexual bias in power. That is, in most cases, sometimes women rule, sometimes men do.

The research team tested five hypotheses to explain sexual biases in dominance relationships and found that female power is primarily observed in species where females are monogamous, of similar size to males, or forage primarily in trees. All of these situations allow females greater discretion when mating with a particular male.

Furthermore, female dominance is also facilitated in situations where females face intense competition for resources, such as in solitary or paired species, and when conflicts between males are less risky for their offspring, for example, because mothers keep them in a safe place while foraging rather than carrying them with them.

In contrast, male dominance prevails in terrestrial species, where males have larger bodies or arms than females, and where they mate with multiple females. "While primate males gain power through physical strength and coercion, female empowerment relies on alternative avenues, such as reproductive strategies to control mating," explains Elise Huchard of the University of Montpellier.

The findings of the study, published in the journal Proceedings of the National Academy of Sciences (PNAS) , have important implications for our understanding of the evolution of social behavior in animals and could also shed light on our understanding of human social dynamics.

According to the researchers, these findings challenge traditional perspectives on the natural origin of gender roles. Humans do not share all the traits that characterize species where males strictly dominate females. Instead, the set of human traits brings them closer to species that display more nuanced relationships, where individuals of both sexes can become dominant. Consequently, the authors say, arguments that present human patriarchy as a legacy from primates appear flawed, and gender relations should be considered in relation to their social and ecological contexts.

"It's very interesting that in most primate populations, there's no clear dominance of one sex over the other. But when it does occur, it's because one sex dominates the other in reproductive control. This control is achieved in a variety of ways: from being able to flee from unwanted suitors to living in a monogamous rather than a polygamous society," Antonio J. Osuna Mascaró, a researcher specializing in animal cognition at the University of Veterinary Medicine in Vienna (Austria), explains to the Science Media Centre (SMC) .

Mascaró also highlights how abandoning arboreal life has favored male dominance. "The inability of females to escape among the branches, the possibility of significant size differences between males and females, the development of 'weapons' (such as tusks), and other traits resulting from life at ground level have given males a certain advantage over females," he continues.

The researcher emphasizes how the study views bonobos "as an oddity." For a long time, it has been assumed that the origin of female dominance in bonobos was due to the coalitions they are able to form to confront males, "but, after studying the 121 species analyzed in this study, it appears that female coalitions are neither necessary nor sufficient to explain female dominance. It seems that bonobos are an exception, a oddity among primates, not because females dominate males (because this occurs in many other species, as shown here), but because of the way in which they have achieved it."