The connection between aggressive sexuality, hunting, domestic violence, and fighting?

25th March 2011

 Humans are animals who have evolved just like every other organism, with selection favoring particular traits over others.”

Maryanski, A 1994

Fifty years ago, ethnologist Konrad Lorenz placed the human aggressive instinct firmly in the context of animal aggression arguing that human beings share a general instinct for aggressive behavior with other animals. (Wilson, 2006, p. 175) In Demonic Males, Professor Richard Wrangham drawing on his own field observations and examples from a number of other sources explored a similar question. He describes how gangs of male chimpanzees hunt, raid and engage in lethal conflict with other males, often over territory, but they have also been found at times to rape females. These kinds of behavior, are not limited to chimpanzees but are exhibited in one form or another by all primates, especially the great apes. Wrangham believes that these behavioral patterns were developed in the common ancestors of chimpanzees and humans, and that they have persisted through five million years of human evolution to the present day, forming the instinctual basis for much of the inter-group aggression, including warfare, that are exhibited in today’s modern societies. (Wrangham, 1996, p61)

Wrangham writes that, a group of chimpanzees setting off to attack a neighboring male exhibit particular behavioral patterns. In contrast to their typical boisterous conduct, they walk silently through the jungle in single file in what primatologists refer to as a “Border Patrol”. Despite his criticism of Wrangham’s ideas Watts reported similar behavioral observations. Watts says that, when following a group of males, they “will switch into what we call patrol mode. They’ll go silent, which is unusual for chimps, and just look and listen. When they hear neighboring chimps, they respond in a pretty predictable way. If there are just a few chimps in the group, for instance, they’ll quietly move back toward the center of their own territory. If it’s a big group, they’ll respond vocally and listen to the responses. If they decide they are evenly matched, that can lead to major aggression. They’ll chase down, surround, and attack rivals. Sometimes they kill them.” (Watts in King, 2007, pp.14-15) The resulting kill is a “Lethal Raid”. Chimpanzees kill males in other groups to gain access to food in their territory and, by eliminating rival males, increase their chances of sexual selection by preventing them from being able to mate with their females. Sometimes the victor “persuades” the females whose males they have killed to join their group.

During the 1970’s Wrangham and Goodall recorded observations on one particular group of chimpanzees that divided into two distinct factions. The members of one group killed every male and some of the females in the other. The victims had until recently been their companions. (Wrangham, 1996 p. 7; Goodall, 2003) From these observations and others, Wrangham went on to develop a theory that would explain human violence based on the aggression he had witnessed. Beginning by pointing out, that humans are hardly a peaceful species, Wrangham constructed a theory that he calls the Demonic Male Hypothesis, arguing that human males and chimps share a tendency to be aggressive with our closest common ancestor. Humans are related more closely to chimpanzees than chimpanzees are to gorillas, which, Wrangham and Peterson claim allows chimpanzees and other ape species that seem to have changed little in 10 or even 15 million years to be viewed as “time machines,” taking us back to the origins of behavior that we now consider uniquely human. (Wrangham, 1996, p.41-43) Silverberg and Gray however disagree, they state, that there is no single pattern of antagonistic behavior among nonhuman primates and that the importance of dominance, violence, reconciliation and so on varies greatly among different species and among different populations of the same species. (Silverberg & Gray, 1992, p. 24) All agree however that at the very least killing a neighbor reduces competition over resources. (Wrangham 1986, p.165)

Chimpanzees and humans share upwards of 98.5 percent of their DNA and as a result have many attributes in common. Both humans and chimpanzees hunt and males show a strong desire to form alliances against other males while maneuvering for greater status. The “alpha male” of any group receives more female attention as well as the respect of his troupe, who, frequently plot and form alliances to undermine this authority. What most male chimpanzees strive for says, Wrangham, is being on top, the one position where they will never have to grovel. It is the difficulty in getting there that induces aggression. (Wrangham, 1996, p.191) It has also been found that male chimpanzees batter females into submission, proving their physical and sexual dominance through violent displays and occasional rapes. The occurrence of rape as an ordinary part of a species behavior implies that it is an evolved adaptation to something in their biology. Wrangham, 1996, p.132) Wrangham suggests that human-chimpanzee shared traits stem from a common ancestor, which lived about six million years ago, and evolved before the two species separated. Pride is another legacy of sexual selection (Wrangham, 1996, p.192)

Twenty years ago researchers discovered that one feature of this shared behavior is the disposition of adult male chimpanzees toward the attacking, maiming and killing of other adult male chimpanzees discovered near their territory. Defense of territory is widespread among many species; the kasekla chimpanzees observed were doing more than defending. They didn’t wait to be alerted to the presence of intruders. They sometimes moved right through the border zones and penetrated half a mile or more into neighboring land. Hey did no feeding on these ventures. And three times I saw them attack lone neighbors. So they seemed to be looking for encounters in the neighboring range. These expeditions were different from mere defense, or even border patrols. These were raids. (Wrangham, 1996, p.14) Among humans and chimpanzees male coalitionary groups often go beyond defense to include unprovoked aggression. (Wrangham, 1996, p.233) Male chimpanzees will organize raiding parties to seek out isolated members of other rival chimpanzee groups before moving in for the kill. The situation in our evolutionary past was no different, according to Wrangham, that chimpanzees and humans kill members of neighboring groups of their own species is a startling exception to the normal rule for animals. Add our close genetic relationship to these apes and we face the possibility that inter-group aggression in our two species has a common origin. (Wrangham, 1996, p.61)

Contemporary hunter-gatherer tribes continue to fight for food, women and status, each displaying that a key aspect of a lethal raid is affording party members greater advantage while decreasing risks to themselves. As social strategists all primates seem to evaluate the costs and benefits of different social behaviors in obtaining desired resources or outcomes. Violent episodes according to Silverberg & Gray are not the result of simply loosing control or of animal instinct overwhelming the fragile boundaries of sociability and civilization. “Violence is a tactic that is used in social interaction, one that is used rarely because of its potential high costs can serve to make it less effective than other tactics in most circumstances.” (Silverberg & Gray, 1992, p.2, 6) The appetite for engagement, the excited assembly of a war party, the stealthy raid, the discovery of an enemy and the quick estimation of odds, the kill, and the escape are common elements within societies that make intercommunity violence possible. (Wrangham, 1996, p.71)

In the Amazon rainforest, the Yanomamo tribes who live in southern Venezuela and the adjacent part of Brazil are renowned for their intense warfare. Within these tribes inter-village raiding in which men are killed and women are captured has become a feature of some areas of Yanomamo territory. (Kottak, 2009 p.386) The men of the Yanomamo call themselves waiteri, a title or name that means fierce. Napoleon Chagnon and others have described the wars of the Yanomamo and report that more than one-third of all Yanomami males died violently, often while participating in raiding parties. (Wrangham, 1996, p.64) Yanomamo war takes place when a subgroup of males, in both cases, gangs of roughly a half a dozen, deliberately invades the recognized territory of a neighboring community (Wrangham, 1996, p.69) Of the remaining, forty per cent have undergone a ritual purification and honored as unokaimou, which occurs when they have killed or participated in killing. (Wrangham, 1996, p.68) according to Wrangham, unokais are honored by their societies and ultimately rewarded. Because the Yanamamo culture allows polygyn, the rewards can directly be translated into reproductive terms, ensuring genetic success (Wrangham, 1996, p.68) Williams states that group level adaptations are a reflection of individual selection and contended that all adaptations must relate to reproductive success. (Maryanski, 1994 p. 377)

Wrangham writes that many hunter-gatherer societies follow similar patterns. Ethnographies for 31 hunter-gatherer societies detailed that 64 per cent engage in warfare once every two years and only 10 per cent fight rarely or never. (Wrangham, 1996, p.75) In Australia, aboriginal cave paintings dating back thousands of years document pitched battles fought with spears and boomerangs. Evolutionary theory suggests that any behavior occurring regularly or consistently has a logic embedded in the dynamics of natural selection for reproductive success. (Wrangham, 1996, p.138) According to social biologists, all organisms seek to maximize their reproductive success by any means necessary. (Maryanski, 1994, p.379)

Male aggression has formed the basis of the social structure in the lives of both humans and chimpanzees for thousands of generations. Every documented society has been patriarchal, with males holding many if not most of the dominant hierarchal positions, using their authority to dominate females and eradicate enemies. According to Howard, males fight “neither because they are aggressive nor because they are acquisitive animals, but because they are reasoning ones, because they discern, or believe that they can discern, dangers before they become immediate, the possibility of threats before they are made.” (Howard in Wrangham, 1996, p.192). There is no doubt that chimpanzees and humans exhibit a capacity at times toward violence. Wars, genocides, rapes and riots are part of a despondent legacy of human activity throughout history, and clearly coded into human nature itself. The evidence suggests that the wars or war-like violence, perpetrated predominantly by males is a genetic characteristic of Homo sapiens and their human and non-human ancestors, and that it is the male propensity toward violence that serves the interests, not only of the warriors themselves, but also of the larger communities in which they live.


King, S.C., 2007, Seeds of War, AuthorHouse, Bloomington, IN, USA. Ch.2 Our Chimpanzee Family Tree, p. 9-15

Darwin, C., 2003, The Origin of Species, Signet Classics Printing, Penguin, New York, N.Y.

Fossey, D., 1988, Gorillas in the Mist, Penguin, London, U.K.

Goodall, J., 2002, My Life with the Chimpanzees, Aladdin, New York, N.Y.

Kottak, C.P., 2009, Anthropology: The Exploration of Human Diversity, 13th Edn., McGraw-Hill, New York, N.Y.

Maryanski, A 1994, ‘The pursuit of human nature in sociobiology and evolutionary sociology’, Sociological Perspectives, vol. 37, no. 3, pp. 375-389

Silverberg, J & Gray, JP., 1992, ‘Violence and peacefulness as behavioral potentialities of primates’, in J Silverberg & JP Gray (eds.), Aggression and peacefulness in humans and other primates, Oxford University Press, New York, pp. 1-36

Stanford, C.B., 1998, ‘The social behaviour of chimpanzees and bonobos’, Current Anthropology, vol. 39, no. 4, pp. 399-420.

Wrangham, R. & Peterson, D, 1996, Demonic Males: Apes and the Origins of Human Violence, Houghton Mifflin, New York, N.Y.

Wilson, E.O., 2006, Nature Revealed: Selected Writings 1949-2006, The John Hopkins University Press, Baltimore, Maryland.




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