We have completed maintenance on DiscoverMagazine.com and action may be required on your account. Learn More

Apes of Wrath

By Barbara Smuts
Aug 1, 1995 5:00 AMNov 12, 2019 4:29 AM


Sign up for our email newsletter for the latest science news

Nearly 20 years ago I spent a morning dashing up and down the hills of Gombe National Park in Tanzania, trying to keep up with an energetic young female chimpanzee, the focus of my observations for the day. On her rear end she sported the small, bright pink swelling characteristic of the early stages of estrus, the period when female mammals are fertile and sexually receptive. For some hours our run through the park was conducted in quiet, but then, suddenly, a chorus of male chimpanzee pant hoots shattered the tranquillity of the forest. My female rushed forward to join the males. She greeted each of them, bowing and then turning to present her swelling for inspection. The males examined her per- functorily and resumed grooming one another, showing no further interest.

At first I was surprised by their indifference to a potential mate. Then I realized that it would be many days before the female’s swelling blossomed into the large, shiny sphere that signals ovulation. In a week or two, I thought, these same males will be vying intensely for a chance to mate with her.

The attack came without warning. One of the males charged toward us, hair on end, looking twice as large as my small female and enraged. As he rushed by he picked her up, hurled her to the ground, and pummeled her. She cringed and screamed. He ran off, rejoining the other males seconds later as if nothing had happened. It was not so easy for the female to return to normal. She whimpered and darted nervous glances at her attacker, as if worried that he might renew his assault.

In the years that followed I witnessed many similar attacks by males against females, among a variety of Old World primates, and eventually I found this sort of aggression against females so puzzling that I began to study it systematically--something that has rarely been done. My long-term research on olive baboons in Kenya showed that, on average, each pregnant or lactating female was attacked by an adult male about once a week and seriously injured about once a year. Estrous females were the target of even more aggression. The obvious question was, Why?

In the late 1970s, while I was in Africa among the baboons, feminists back in the United States were turning their attention to male violence against women. Their concern stimulated a wave of research documenting disturbingly high levels of battering, rape, sexual harassment, and murder. But although scientists investigated this kind of behavior from many perspectives, they mostly ignored the existence of similar behavior in other animals. My observations over the years have convinced me that a deeper understanding of male aggression against females in other species can help us understand its counterpart in our own.

Researchers have observed various male animals--including insects, birds, and mammals--chasing, threatening, and attacking females. Unfortunately, because scientists have rarely studied such aggression in detail, we do not know exactly how common it is. But the males of many of these species are most aggressive toward potential mates, which suggests that they sometimes use violence to gain sexual access.

Jane Goodall provides us with a compelling example of how males use violence to get sex. In her 1986 book, The Chimpanzees of Gombe, Goodall describes the chimpanzee dating game. In one of several scenarios, males gather around attractive estrous females and try to lure them away from other males for a one-on-one sexual expedition that may last for days or weeks. But females find some suitors more appealing than others and often resist the advances of less desirable males. Males often rely on aggression to counter female resistance. For example, Goodall describes how Evered, in persuading a reluctant Winkle to accompany him into the forest, attacked her six times over the course of five hours, twice severely.

Sometimes, as I saw in Gombe, a male chimpanzee even attacks an estrous female days before he tries to mate with her. Goodall thinks that a male uses such aggression to train a female to fear him so that she will be more likely to surrender to his subsequent sexual advances. Similarly, male hamadryas baboons, who form small harems by kidnapping child brides, maintain a tight rein over their females through threats and intimidation. If, when another male is nearby, a hamadryas female strays even a few feet from her mate, he shoots her a threatening stare and raises his brows. She usually responds by rushing to his side; if not, he bites the back of her neck. The neck bite is ritualized--the male does not actually sink his razor-sharp canines into her flesh--but the threat of injury is clear. By repeating this behavior hundreds of times, the male lays claim to particular females months or even years before mating with them. When a female comes into estrus, she solicits sex only from her harem master, and other males rarely challenge his sexual rights to her.

These chimpanzee and hamadryas males are practicing sexual coercion: male use of force to increase the chances that a female victim will mate with him, or to decrease the chances that she will mate with someone else. But sexual coercion is much more common in some primate species than in others. Orangutans and chimpanzees are the only nonhuman primates whose males in the wild force females to copulate, while males of several other species, such as vervet monkeys and bonobos (pygmy chimpanzees), rarely if ever try to coerce females sexually. Between the two extremes lie many species, like hamadryas baboons, in which males do not force copulation but nonetheless use threats and intimidation to get sex.

These dramatic differences between species provide an opportunity to investigate which factors promote or inhibit sexual coercion. For example, we might expect to find more of it in species in which males are much larger than females--and we do. However, size differences between the sexes are far from the whole story. Chimpanzee and bonobo males both have only a slight size advantage, yet while male chimps frequently resort to force, male bonobos treat the fair sex with more respect. Clearly, then, although size matters, so do other factors. In particular, the social relationships females form with other females and with males appear to be as important.

In some species, females remain in their birth communities their whole lives, joining forces with related females to defend vital food resources against other females. In such female bonded species, females also form alliances against aggressive males. Vervet monkeys are one such species, and among these small and exceptionally feisty African monkeys, related females gang up against males. High-ranking females use their dense network of female alliances to rule the troop; although smaller than males, they slap persistent suitors away like annoying flies. Researchers have observed similar alliances in many other female-bonded species, including other Old World monkeys such as macaques, olive baboons, patas and rhesus monkeys, and gray langurs; New World monkeys such as the capuchin; and prosimians such as the ring-tailed lemur.

Females in other species leave their birth communities at adolescence and spend the rest of their lives cut off from their female kin. In most such species, females do not form strong bonds with other females and rarely support one another against males. Both chimpanzees and hamadryas baboons exhibit this pattern, and, as we saw earlier, in both species females submit to sexual control by males.

This contrast between female-bonded species, in which related females gang together to thwart males, and non-female-bonded species, in which they don’t, breaks down when we come to the bonobo. Female bonobos, like their close relatives the chimpanzees, leave their kin and live as adults with unrelated females. Recent field studies show that these unrelated females hang out together and engage in frequent homoerotic behavior, in which they embrace face-to-face and rapidly rub their genitals together; sex seems to cement their bonds. Examining these studies in the context of my own research has convinced me that one way females use these bonds is to form alliances against males, and that, as a consequence, male bonobos do not dominate females or attempt to coerce them sexually. How and why female bonobos, but not chimpanzees, came up with this solution to male violence remains a mystery.

Female primates also use relationships with males to help protect themselves against sexual coercion. Among olive baboons, each adult female typically forms long-lasting friendships with a few of the many males in her troop. When a male baboon assaults a female, another male often comes to her rescue; in my troop, nine times out of ten the protector was a friend of the female’s. In return for his protection, the defender may enjoy her sexual favors the next time she comes into estrus. There is a dark side to this picture, however. Male baboons frequently threaten or attack their female friends--when, for example, one tries to form a friendship with a new male. Other males apparently recognize friendships and rarely intervene. The female, then, becomes less vulnerable to aggression from males in general, but more vulnerable to aggression from her male friends.

As a final example, consider orangutans. Because their food grows so sparsely, adult females rarely travel with anyone but their dependent offspring. But orangutan females routinely fall victim to forced copulation. Female orangutans, it seems, pay a high price for their solitude.

Some of the factors that influence female vulnerability to male sexual coercion in different species may also help explain such variation among different groups in the same species. For example, in a group of chimpanzees in the Taï Forest in the Ivory Coast, females form closer bonds with one another than do females at Gombe. Taï females may consequently have more egalitarian relationships with males than their Gombe counterparts do.

Such differences between groups especially characterize humans. Among the South American Yanomamö, for instance, men frequently abduct and rape women from neighboring villages and severely beat their wives for suspected adultery. However, among the Aka people of the Central African Republic, male aggression against women has never been observed. Most human societies, of course, fall between these two extremes.

How are we to account for such variation? The same social factors that help explain how sexual coercion differs among nonhuman primates may deepen our understanding of how it varies across different groups of people. In most traditional human societies, a woman leaves her birth community when she marries and goes to live with her husband and his relatives. Without strong bonds to close female kin, she will probably be in danger of sexual coercion. The presence of close female kin, though, may protect her. For example, in a community in Belize, women live near their female relatives. A man will sometimes beat his wife if he becomes jealous or suspects her of infidelity, but when this happens, onlookers run to tell her female kin. Their arrival on the scene, combined with the presence of other glaring women, usually shames the man enough to stop his aggression.

Even in societies in which women live away from their families, kin may provide protection against abusive husbands, though how much protection varies dramatically from one society to the next. In some societies a woman’s kin, including her father and brothers, consistently support her against an abusive husband, while in others they rarely help her. Why?

The key may lie in patterns of male-male relationships. Alliances between males are much more highly developed in humans than in other primates, and men frequently rely on such alliances to compete successfully against other men. They often gain more by supporting their male allies than they do by supporting female kin. In addition, men often use their alliances to defeat rivals and abduct or rape their women, as painfully illustrated by recent events in Bosnia. When women live far from close kin, among men who value their alliances with other men more than their bonds with women, they may be even more vulnerable to sexual coercion than many nonhuman primate females.

Like nonhuman primate females, many women form bonds with unrelated males who may protect them from other males. However, reliance on men exacts a cost--women and other primate females often must submit to control by their protectors. Such control is more elaborate in humans because allied men agree to honor one another’s proprietary rights over women. In most of the world’s cultures, marriage involves not only the exclusion of other men from sexual access to a man’s wife--which protects the woman against rape by other men--but also entails the husband’s right to complete control over his wife’s sexual life, including the right to punish her for real or suspected adultery, to have sex with her whenever he wants, and even to restrict her contact with other people, especially men.

In modern industrial society, many men--perhaps most--maintain such traditional notions of marriage. At the same time, many of the traditional sources of support for women, including censure of abusive husbands by the woman’s kinfolk or other community members, are eroding as more and more people end up without nearby kin or long-term neighbors. The increased vulnerability of women isolated from their birth communities, however, is not just a by-product of modern living. Historically, in highly patriarchal societies like those found in China and northern India, married women lived in households ruled by their husband’s mother and male kin, and their ties with their own kin were virtually severed. In these societies, today as in the past, the husband’s female kin often view the wife as a competitor for resources. Not only do they fail to support her against male coercive control, but they sometimes actively encourage it. This scenario illustrates an important point: women do not invariably support other women against men, in part because women may perceive their interests as best served through alliances with men, not with other women. When men have most of the power and control most of the resources, this looks like a realistic assessment.

Decreasing women’s vulnerability to sexual coercion, then, may require fundamental changes in social alliances. Women gave voice to this essential truth with the slogan SISTERHOOD IS POWERFUL--a reference to the importance of women’s ability to cooperate with unrelated women as if they were indeed sisters. However, among humans, the male-dominant social system derives support from political, economic, legal, and ideological institutions that other primates can’t even dream of. Freedom from male control--including male sexual coercion--therefore requires women to form alliances with one another (and with like-minded men) on a scale beyond that shown by nonhuman primates and humans in the past. Although knowledge of other primates can provide inspiration for this task, its achievement depends on the uniquely human ability to envision a future different from anything that has gone before.

1 free article left
Want More? Get unlimited access for as low as $1.99/month

Already a subscriber?

Register or Log In

1 free articleSubscribe
Discover Magazine Logo
Want more?

Keep reading for as low as $1.99!


Already a subscriber?

Register or Log In

More From Discover
Recommendations From Our Store
Shop Now
Stay Curious
Our List

Sign up for our weekly science updates.

To The Magazine

Save up to 40% off the cover price when you subscribe to Discover magazine.

Copyright © 2024 Kalmbach Media Co.