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What Primates Can Teach Us About Gender

Frans de Waal’s new book "Different" shows us how similar we really are.

Key points

  • Sex differences are biological, whereas differences in gender expression are cultural.
  • Evolutionarily, humans are equally related to patriarchal chimpanzees and matriarchal bonobos.
  • Understanding natural variability in primate sexual behavior and gender expression can help us become more understanding of our own differences.

I recently had the honor of speaking with Frans de Waal, one of the world’s foremost experts in primatology, on The Nature & Nurture Podcast. We spoke about his new book Different: Gender Through the Eyes of a Primatologist. Despite its name, my takeaway from Different was how similar we all really are: not just individuals of the same sex, or even all humans cross-culturally, but humans and our closest primate relatives, chimpanzees and bonobos.

Chimpanzees and Bonobos

Drawing on decades of research and fieldwork, de Waal describes how chimps and bonobos, who on the surface look quite similar, are behaviorally polar opposites: Chimpanzees are male-dominated, competitive, territorial, and sometimes violent. Bonobos are female-dominated, peaceful, and highly sexual. Humans fall somewhere in the middle. We now know that genetically and evolutionarily, humans are equally related to chimpanzees and bonobos. We all diverged about 6 million years ago, and share over 99% of our DNA.

De Waal describes how, historically, bonobos were overlooked; for a long time they were not recognized as their own species but as “pygmy chimpanzees.” In the late 1800s and early 1900s, when biology and primatology was exclusively male-dominated, the prevailing narrative was that humans had conquered our way to the top of the food chain, and that patriarchal aggression was the natural way of life. Violence in chimpanzees was sensationalized by the media, and biologists even speculated that we had evolved our capacity for cooperation not because it pays to be altruistic, but because it was necessary for wartime strategizing.

Shaped by Victorian-era presuppositions about coy femininity, as well as a lack of female representation in the field, the role of females in primate evolution was long overlooked. This began to change in the 1950s when the first female primatologists, such as Jane Goodall, came onto the scene with fresh eyes. We began to recognize that violence is not the only way to the top, and that bonobos had evolved stable, peaceful, female-dominated societies. Even in chimpanzees, we began to recognize the role that status competition played in females, too; the alpha female can sometimes have as much or more power than the alpha male. (See de Waal’s Mama’s Last Hug for stories about the long-reigning alpha female chimpanzee, Mama.)

Sex Differences in Humans and Primates

It’s clear that our own biases had shaped our conceptions about primatology for many decades, but, as de Waal takes great care to point out, the scientific process itself remains objective. Feminist perspectives in primatology taught of where to look for new data, but once that data was collected, it spoke for itself.

Similarly, our evolving conceptions of gender helped provide us with a new framework with which to study sex differences. Broadly speaking, sex is biological and gender is cultural. This nature-nurture nuance allows us to ask questions about which sex and gender differences are innate and which are socially constructed.

One example de Waal opens his book with is children’s toy preferences. Cars and the color blue are typically marketed for boys, whereas dolls and the color pink are typically marketed for girls. Yet infants show no preferences for colors, and in the pre-World War II era, pink was regarded as traditionally masculine and blue as traditionally feminine. Color preferences are an example of a gender difference that is entirely socially constructed.

Interestingly, this does not seem to be the case with toy preferences. Cross-culturally, young boys prefer cars and girls prefer dolls. This is even true across species; De Waal describes how young female primates are fascinated with dolls and babies, and will even pretend-play mother with objects such as rocks. Male primates are disinterested in dolls, and will sometimes rip them apart to inspect their insides.

Whether or not these represent innate biological differences, at the very least, chimps seem hardwired to emulate same-sex adults. For example, de Waal describes how young chimpanzee females closely emulate their mothers’ termite fishing techniques, whereas young males prefer to go off and hunt with other males. Even in the seemingly innate role of motherhood, new chimpanzee mothers will not know how to properly nurse their young without proper role-models. In this sense, gender roles in primates can be thought of as reducing the amount of trial-and-error that would otherwise result from biological necessity.

Sexual Competition

Wherever gender differences arise, they appear to be primarily related to sex—both biological sex and the act itself. Beyond obvious functional differences in genitalia, de Waal describes how sexual dimorphism arises as a function of intrasexual (typically male-male) competition. Gorillas, which form harems of several females per male, see extreme sexual competition between males. Males have evolved to be twice the size of females, who have no need to fight. Bonobos, by contrast, have sex with everyone (including same-sex sex, as a form of social bonding) and thus have comparatively little sexual competition, and sexual dimorphism (though they have evolved much larger testes than humans because of intense sperm competition). Human males are, on average, 20% larger than females, indicating a moderate degree of intrasexual competition in our evolutionary past.

Behaviorally, this increased intrasexual rivalry may be why men have evolved to be more violent (most violent crimes are committed by men) and are typically regarded as valuing status more. However, de Waal points out that it is a myth that men are more aggressive and competitive than women: rather, our competition takes different forms. In both humans and chimpanzees, male dominance disputes tend to be more overtly aggressive, whereas female disputes tend to be more subtle and relational: Think Mean Girls.

Beyond the Binary

While most gender differences can be understood in the context of sex, things get more complicated when the two are decoupled, such as in the case of nonbinary and transgender persons. However, these do not appear to be forms of identity unique to humans. De Waal describes one female chimpanzee he studied, Donna. Donna never had children or engaged in the political power-plays typical of females. She would puff up her hair and call out like males during their status displays. Yet, she was not aggressive, and did not fight with males for dominance. Neither was she low-ranking; she was respected by her peers, but different. Put simply, Donna was noncomforming, but accepted.

Different taught me that we – humans of all genders, as well as nonhuman primates – are really not that different. Primatology teaches us about ourselves through our closest living relatives, and we find evidence for both the more egalitarian, bonobo-like, peaceful society to strive for, as well as the roots of our chimpanzee-like, sex-specific tendencies for aggression and dominance. Above all, de Waal stresses that we must not confuse is with ought: We are not defined solely by our evolutionary past, but we must understand our innate differences in order to become the species we wish to be.