Battle of the Sexes: Economy of Aggression or Sex?
Opinion Essay for Human Cognitive Evolution (EVANTH 260) taught by Dr. Brian Hare at Duke University
March 2025Inspired by lecture and discussion on the distinct social behaviors of our two closest primate relatives: Chimpanzees and Bonobos
Machiavelli famously said: “It is better to be feared than loved, if you cannot be both.” In the animal kingdom, the struggle for dominance often appears as a fierce battle — but what if that battle is not always fought with violence? Instead, what if it is won through cooperation, or even through something as unexpected as sexual behavior? When it comes to understanding aggression and social dynamics, the contrast between chimpanzees and bonobos presents a striking case of evolution, in which two closely related species differ profoundly in how they maintain group cohesion and social order. Chimpanzees, while an incredibly complex species with advanced cognitive abilities and bold and lovable personalities, have a darker, male-dominanted side, characterized by aggressive behavior and xenophobia, in which dominance is enforced through the threat of violence. Bonobos, on the other hand, are female-dominant and known for their significantly more peaceful society, characterized by tolerance and facilitated by sociosexual bonding and conflict resolution. This raises the question, which strategy is more effective in maintaining relationships and preventing fragmentation within a complex social group: aggression or sex? While impossible to say one species is, in any way, better than another, this essay defends my humble opinion that a sex-based economy, as in bonobos, is arguably more effective at maintaining a healthy group dynamic than an aggression-based economy. Drawing parallels to human behavior, I find that, contrary to what Machievalli said, love may be more powerful than fear in shaping a healthy society.
Chimpanzees and Bonobos are our closest living relatives, having shared a common ancestor with us humans approximately 5 to 7 million years ago. We share about 97.5% of our DNA with both species, making us equally related to both Chimpanzees and Bonobos. Even more so, bonobos and chimpanzees are more closely related to each other than to any of other species, including humans. The two species share many similarities, including physical traits, behaviors and genetic makeup. Chimpanzees and Bonobos both live in complex social groups where individuals form strong bonds, engage in social grooming and cooperate within their groups. In both species, individuals participate in social alliances and form coalitions, which are crucial for maintaining group cohesion and social hierarchies.
Yet somehow, despite this relatedness, chimpanzees and bonobos are vastly different in their social organization and behavior, a true reflection of the 1-2 million years of independent evolution between them. Most significantly, Chimpanzees and Bonobos differ significantly in their social dynamics and approach to conflict and rank.
Chimpanzees, with their aggressive hierarchies and violent power struggles, seem to echo humanity’s darker impulses. In Chimpanzee society, males often rise to the top of the social hierarchy through displays of strength, intimidation and violence, ensuring that their power is respected and feared by others. Within a chimpanzee group there is a male-dominanted, species-specific economy in which aggression and violence serve as currency. Male chimpanzees engage in territorial defense, border control, and group hunting, as well as (and uniquely) warfare and lethal raiding. In this sense, fear of dominant males plays a critical role in maintaining control, as subordinates are unlikely to challenge a dominant individual. Operating in the competitive chimpanzee environment where status and survival are determined by physical power and dominance, the Machievellian approach prevails.
This is sometimes true for humans as well, as we historically have and will continue to engage in warfare and strategic violence over territory, resources or political power. And like Chimpanzees, the tendency for aggression is deeply rooted in patriarchy, where males compete for dominance within a social group or organization. The evolutionary basis for this is sexual selection, and competition for mating opportunities. The Parental Investment Theory posits that because women invest more in offspring (ie, pregnancy, childbirth and nurturing), they are more selective in choosing mates; while males, have less investment in reproduction, are inclined to compete for access to multiple mates. This intrasexual competition fosters aggressive behavior as a means of establishing and maintaining dominance, which, to females of many species, is a direct indicator of genetic superiority.
In human society, this biological drive for reproductive success lingers, and manifests itself as both direct and indirect competition for money, power and status. Evidence comes from the rich history of male-dominated political, economic and social systems driven by fear and control, with clear dominance. In medieval Europe, for example, many rulers adopted a strategy of fear to maintain their dominance over their subjects. The Machiavellian approach emphasizes the use of coercion, manipulation, fear tactics and strategic deception as means of acquiring and securing status, the modern-human equivalent of victory within chimpanzee intra competition.
However, as we’ve seen in human history, the Machiavellian approach, while effective in the short term, often leads to unstable societies. The Roman Empire, for example, saw the rise of brutal emperors who maintained control through fear, but these regimes were often short-lived, and internal divisions and civil wars contributed to the empire’s eventual decline. This might suggest that a system based on aggressive displays of dominance ultimately breeds resentment and distrust among subordinates. Dominant males may face challenges to their authority, as fear may be effective in preventing immediate rebellion and insubordination, but it is less effective in fostering loyalty and genuine cooperation. The resulting insecurity intrinsic to Chimpanzee social hierarchies manifests in violent power struggles as individuals or coalitions may attempt to overthrow the current leader.
In contrast to chimpanzees, bonobo societies are characterized by a more peaceful, female led society where sexual behavior is central to conflict resolution, and cooperation prevails over violence. Rather than relying on aggression and violence to establish dominance, female bonobos invest in their social bonds to maintain harmony within the group. Bonobos highlight an alternative approach to social organization that challenges the male-dominated, aggressive dynamics seen in many primate species, including humans.
In bonobo groups, female dominance is reinforced by their ability to control key resources like food and mates. Unlike chimpanzees, where males typically dominate and maintain power through aggression, bonobos achieve social cohesion and stability through female leadership. Males, while still involved in the social structure, tend to be subordinate to females, and their status is often determined by relations and the alliances they form with females, rather than through displays of aggression or dominance.
Female bonobos also form strong alliances with one another, which help to mediate conflicts. In some cases, they even work together to keep males in check, preventing them from dominating the social structure.
The Bonobo matriarchy may also be a result of sexual selection, reflecting significant differences in evolutionary pressures on females compared to that of males. Females enjoy secure relationships that provide them ample access to resources, meaning survival depends on social integration and reputation and not size or strength, which fosters the cooperative, peaceful environment that characterizes bonobo societies. Females can prioritize social bonds, cooperation, and peaceful resolution of conflicts, rather than rewarding violent or aggressive displays that may destabilize the group.
Famously, socio-sexual behavior plays a significant role in maintenance of bonobo societies. Bonobos use sexual interactions not only for reproduction but also as a means of conflict resolution, stress alleviation, and social bonding. When tensions arise between individual bonobos, rather than resulting to violence in which the winner can be predicted by size and dominance, bonobos, particularly females, may engage in genital-to-genital rubbing to diffuse potential aggression or disputes.
It is important to note that, while Chimpanzees engage in aggressive behavior significantly more often than Bonobos, Bonobos are still capable of aggressive disputes. The key difference is severity, as no Bonobo has ever been known to kill another Bonobo, and they don’t rely on aggressive episodes to shape their hierarchy. Additionally, Chimpanzees of course do also have sex and form strong attachments to each other, but similarly, these attachments have little to do with the social hierarchy enforced by males.
While the chimpanzee model may emphasize competitive individualism and power, the bonobo model demonstrates the benefits of cooperation, empathy, and peaceful conflict resolution. In terms of maintaining social relationships and group cohesion, the female-led bonobo society arguably offers a more sustainable approach. By prioritizing social bonds and reducing the need for aggression, bonobos create a more stable and harmonious social environment.
The debate between male-dominated Chimpanzee societies and female-led Bonobo societies is an interesting one, and its essence is the means through which the group enforces its organization, particularly their social hierarchies, coalitions and resource distribution.
Chimpanzee societies rely on principles parallel to those behind the darker side of human history, while Bonobos challenge us to consider the benefits of groups built on mutual trust maintained through pro-social interactions. While I’m of the opinion that bonobo sex and friendship is a much better currency than chimpanzee aggression and dominance, perhaps the real lesson is much less about which is more effective in their societies, but about which is more effective in ours. Ultimately, investigation of the lives of our two closest species involves recognizing that both male aggression and female cooperation play important roles in our evolutionary history with the potential to inform our approaches to many different aspects of our societies. There are lessons to be learned from both Chimpanzees and Bonobos about the balance between aggression and cooperation which may be applied to our own lives, with the potential to improve human social dynamics and build healthier societies.
