Mountain Gorillas Teach a Lesson about Gendered Behavior

By Nathan H. Lents and Stacy Rosenbaum

[A longer version of this post can be found here.]

The mountain gorillas of Virunga National Park in Rwanda have been under continuous intense scientific scrutiny since George Schaller and Dian Fossey began their pioneering work in the 1950s. Fossey was the subject of the Oscar-nominated biopic Gorillas in the Mist.

Dian Fossey observing Mountain Gorillas Image Source: Dian Fossey Gorilla Fund International

Male gorillas are more than twice as large as females, underscoring their evolutionary legacy of male contest competition and polygyny. Indeed, gorillas were long thought to exist almost exclusively in harems, small multi-female groups led by one powerful silverback. Upon reaching adulthood, young males typically leave their birth group and go through a solitary period before attempting to take over a harem or start a group of their own. Most are not successful.

Beginning in the 1990s, some younger males stopped leaving their groups. Scientists began observing very large groups including several adult males and females living together in relative harmony. Some groups hosted up to nine adult males, and one group topped out at 66 total animals. Twenty years in, this trend shows no sign of reversing and currently involves one-fourth of the mountain gorilla population at Virunga.

A Mountain Gorilla community in Virunga National Park Photo Credit: Dian Fossey Gorilla Fund International
A Mountain Gorilla community in Virunga National Park
Photo Credit: Dian Fossey Gorilla Fund International

This raises very pointed questions for the field of evolutionary psychology. Central to evolutionary psychological theory is the notion that behaviors are the product of natural selective forces that reward reproductive success. Many controversial corollaries have sprung from that seemingly straightforward claim, including that some behavioral distinctions between men and women might be the result of innate, naturally selected differences. Intangible phenomena like professional ambition, competitive tendencies, and desire for a rewarding family life, along with more concrete cognitive abilities such as spatial and quantitative reasoning, are sometimes invoked in the otherwise thoughtful conversations about why we don’t see more female astrophysicists on the Harvard faculty.

The problem, according to some, is that social engineering has costs. If men are, on average, naturally better than women at math, enforcing gender parity in top mathematics positions would mean elevating some of lesser natural ability over some with greater ability. The effect for society is a net loss in the fruits of our collective mathematics potential.

It is true that humans clearly harbor some average biological differences between the sexes. Male breasts rarely produce milk and women have no equivalent of the prostate gland. While there are some excellent female sprinters that could run circles around most men, the very fastest sprinters are all men and the average man is faster than the average woman.

Behavior, however, stems from the brain and its associated neurochemistry. The notion that brain anatomy is different between the sexes has been roundly discredited. On any one measure, for example the thickness of the corpus collosum, there may be average sex differences, but the ranges within the sexes are bigger than the average difference between them, and the ranges overlap substantially. Crucially, any one individual will exhibit a combination of characteristically male and female measurements for different parts of the brain. There is simply no such thing as a “male brain” and a “female brain,” at least not anatomically.

More to the point, research has yet to exclude environmental causes for the few observed sex differences in cognitive abilities. No child has ever been reared free of the pervasive influence of socially constructed gender norms. As Elizabeth Spelke and many others have shown, even the most feminist parents begin treating their male and female children differently on their first day of life. We are very far from knowing what males and females might naturally aspire to and be capable of, absent the influence of a social environment that shapes them to be, and to want to be, different.

Evolutionary psychology, seemingly the curmudgeon of progressive thinking, may actually provide the answer to the very dilemma it raises. In his passionate attack of “the blank slate,” Steven Pinker convincingly establishes the genetic basis of certain behaviors as drives, instincts, and tendencies that provide a wide, but not infinite, range of possible outcomes. Underneath this is a principle, as simple as it is elegant, that genes plus environment equals behavior.

While blank slate proponents ignore the role of genes in creating behavior, evolutionary psychologists may be underappreciating the role of environment. In their worry about men whose wings are clipped to make room for women, they forget the girls whose preferences are shaped by a world that tells them how cute they are, rather than how strong or how smart. In her new book, Beyond BiofatalismGillian Barker expresses the challenge saliently:

“Evolutionary psychologists focus on the Orwellian threat of overt unhappiness resulting from people’s inability to fulfill their preferences, or from forcible attempts to suppress those preferences, but in so doing, they overlook… the danger of a hidden or cryptic loss of happiness resulting from a limitation of people’s horizons that makes it impossible for them to form certain preferences in the first place.”

When Schaller and Fossey first began, it would have been virtually unimaginable to see six adult male gorillas co-existing, but this is now routine. The mountain gorilla silverbacks even ‘parent’ other males’ infants, and their collective protective abilities mean that infants in groups with more than one male are less likely to die of infanticide than infants born in a group where their father is the only male.

Humans too have accomplished whole-scale behavioral transformations. In fact, in his book, Better Angels of Our Nature: Why Violence Has Declined, Pinker chronicles the steady waning of violent deaths in human societies since the dawn of civilization. The social contract has allowed human beings to dramatically alter the way we interact with one another. Violence, even when warranted, is shunned in our youth and punished harshly in adults. Despite what sensationalist media headlines might have us believe, we are living in the most peaceful time in the history of our species.

What is this if not social engineering? The leviathan restrains our natural instincts toward violence and instead, society redirects those competitive instincts towards sports, professional ambition, and the like. Genes plus environment equals behavior.

The reason we don’t hear any concern about the smothering of our “true nature” as violent apes is obvious: we are all better off for having our behavior shaped in this way. There is nothing ‘unnatural’ about creating a social milieu that discourages violence any more than there is something unnatural about the way that Rwanda’s mountain gorillas are now living.

Once again, a lion of evolutionary psychology, David Buss, has said it best: “Human behavior is enormously flexible – a flexibility afforded by the large number of context-dependent evolved psychological adaptations that can be activated, combined, and sequenced to produce variable adaptive human behavior.”

Photo Credit: Argonne National Laboratory
Photo Credit: Argonne National Laboratory

The sheer rapidity with which women have entered the highest level of the work force, compared to just a generation ago, argues forcefully that professional ambition in women is hardly unnatural. It seems much more likely that keeping women away from professional life was unnatural in the first place. In this light, social efforts to facilitate gender equality and parity may not be coercive social engineering, but its opposite: the removal of coercion that has restrained women for far too long.

Questions of differing potential and preferences will likely persist, but if the mountain gorillas in Rwanda can totally transform their highly gendered social behaviors – and flourish in the process – can we not also?

The answer is simple. Of course we can because we already have.

[The authors do not speak on behalf of the Dian Fossey Gorilla Fund International, which has not endorsed the views represented here.] 

Nathan H. Lents is Professor of Molecular Biology and director of the honors program and the Macaulay Honors College at John Jay College of the City University of New York. He also maintains The Human Evolution Blog and the “Beastly Behavior” blog at Psychology Today.

Stacy Rosenbaum is a postdoctoral fellow at the University of Chicago and the Lincoln Park Zoo. She is author of several papers on mountain gorilla behavior, stemming from her work at the Dian Fossey Gorilla Fund’s Karisoke Research Center in Rwanda.



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