Female alliances conquer bonobo society

In the animal kingdom, strength often decides who eats first, who mates, and who leads. But in the lush forests of the Congo Basin, one species rewrites that rulebook. Bonobos, close cousins of humans, live in communities where the real source of authority isn’t muscle, it’s alliance. And at the heart of it all are the females, whose quiet cooperation reshapes power in ways that surprise even seasoned primatologists. So, in situations where males try to muscle their way in to dominate, before things escalate, females close ranks, restoring order by sisterhood. This kind of scene, repeated over decades of careful observation in different contexts, has led scientists to the discovery that in bonobo society, females often outrank males, even though males are bigger and stronger. How is that possible? A study published in [Communications Biology] provides the clearest answer yet: female coalitions, alliances of two or more females banding together, are the secret to female power in this remarkable species. ### Female power! Across most of the animal kingdom, males hold the upper hand when it comes to dominance. Size and strength usually decide who wins conflicts, and with few exceptions, like spotted hyenas and some lemurs, males are dominant over females. Even in our close relatives, chimpanzees, males almost always outrank females and often use aggression to control access to food and mates. Bonobos (*Pan paniscus*), however, break this rule. Despite being slightly smaller than their male counterparts, female bonobos frequently win fights, take priority access to food, and in many cases, occupy the very top spots in the social hierarchy. It’s one of the rarest phenomena in the mammal world: widespread female dominance in a species with male-biased body size. Why does this happen? Biologists have long debated the answer, proposing three main hypotheses. According to the self-organization hypothesis, power might shift simply because of the momentum of winning or losing. Once individuals start to win fights, they keep winning; losers keep losing. In some species, this can allow females to outrank certain males, especially if there are many males competing against each other. Then, there is the reproductive control hypothesis, which says that if males can’t easily monopolize fertile females (because of hidden ovulation or synchronized breeding), their aggressive strategies may backfire. In such cases, females may gain leverage in the mating game. Finally, biologists proposed the female coalition hypothesis, that is, females may win not by going solo, but by banding together. Through strategic alliances, they can tip the balance of power, especially when males behave aggressively. The new study by Surbeck and his team tested all three, using a dataset spanning 30 years and six wild bonobo communities. The research team, which includes scientists from Harvard University, the Max Planck Institute, Wageningen University, the German Primate Center, and the Royal Zoological Society of Antwerp, gathered data from six communities across three long-term field sites in the Democratic Republic of Congo. Some of these sites, like LuiKotale and Kokolopori, have been studied intensively for decades, with researchers following bonobos from dawn to dusk, recording every squabble, alliance, and reconciliation. Altogether, the dataset included over 1,700 recorded intersexual conflicts, a treasure trove for understanding how power dynamics play out in real life. So, which hypothesis held up? Only one: the female coalition hypothesis. The researchers discovered that bonobo females were far more likely to beat males when they joined forces. In fact, 85% of female coalitions targeted males. Also, in communities where females formed coalitions more often, they consistently ranked higher than males. On average, females won 61% of conflicts with males and outranked about 70% of them. In some communities, every adult female outranked every male. This was not simply a matter of numbers or chance. The team found no evidence that the proportion of males in a group (as predicted by the self-organization hypothesis) influenced female power. Nor did female sexual cycles (as predicted by the reproductive control hypothesis) matter much. Instead, what mattered most was whether females stood together. ### The human connection and the ape contrast Bonobos are one of our two closest living relatives, alongside chimpanzees. And while chimpanzee society is famously male-dominated, sometimes violently so, bonobos show us another path, where cooperation and alliances give females extraordinary influence. This research resonates with themes we humans know well. Across cultures and history, women have often found strength in solidarity, whether in suffrage movements, labor unions, or contemporary advocacy groups. The bonobo story suggests that this isn’t just a cultural accident. It may tap into deep evolutionary strategies where collective support levels the playing field. We would expect that chimpanzees behaved in the same way, but that's not the case. In chimpanzee groups, males rule through aggression and form powerful coalitions with other males. Females, often smaller and isolated from one another, rarely band together. The result is a system where coercion is common, and males monopolize many of the resources. Bonobos, by contrast, have evolved a very different strategy. Female bonding, often reinforced by grooming, food sharing, and even sexual interactions, creates trust and solidarity. When males step out of line, they face not one female, but several. It’s not hard to see why this changes the balance of power. This study strengthens the idea that cooperation, not just competition, can be a decisive evolutionary force. For bonobos, solidarity transforms the social landscape. Also, dominance isn’t only about size or strength. Social strategies, like building alliances, can overturn biological disadvantages. Moreover, variation matters: even among bonobos, not all communities look the same. Some are more female-dominated than others, depending on how often females form coalitions. This shows that social culture can shape biology’s outcomes. Finally, our evolutionary cousins demonstrate that power hierarchies aren’t fixed. The way individuals connect and cooperate can fundamentally shift who holds influence. If you want to learn more, the original article titled "Drivers of Female Power in Bonobos" on [Communications Biology] at . [Communications Biology]: http://dx.doi.org/10.1038/s42003-025-07900-8

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