Chimpanzee and Human Males as Demonic Killers

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One of the new claims to the importance of killing and the biological basis of morality is that of Richard Wrangham and Dale Peterson in their book, Demonic Males: Apes and the Origins of Human Violence. Their argument rests on the fact that 20—25 years ago we thought human aggression was unique because research on the great apes had revealed that those species were basically unaggressive, gentle creatures. Although early theorists proposed that hunting, killing, and extreme aggressive behavior were biological traits inherited from our earliest hunting, hominid ancestors, many anthropologists still believed that patterns of aggression were environmentally and culturally determined—learned behaviors. Our sins were thought by most to be acquired and not inherited characteristics. Our sins were no more original than all the other acquired and culturally transmitted traits manifested by the human species. Wrangham and Peterson argue that new evidence indicates the killer instincts are not unique to humans—we share this characteristic with our nearest relative, the common chimpanzee. In fact it is this inherited propensity for killing that allows hominids and chimps to be such good hunters.

Here's the demonic male theory in a nutshell: The split between humans and common chimpanzees happened at least 8 million years ago. Furthermore, humans may have split from the chimpanzee—bonobo

(pygmy chimp) line after gorillas, with bonobos separating from chimps only 2.5 million years ago. Because a chimp-like being may be the common ancestor of all these forms, and because the earliest australopithecine was quite chimpanzee-like, Wrangham speculates that: "The most reasonable view for the moment is that chimpanzees are . . . an amazingly good model for the ancestor of hominids . . . [and if] we know what our ancestor looked like, naturally we get clues about how it behaved . . . that is, like modern-day chimpanzees."26 Finally, if modern chimpanzees and modern humans share certain behavioral traits, these traits have "long evolutionary roots" and are likely to be fixed, biologically inherited components of our nature and not culturally determined.

Further to the demonic male theory, there are a number of cultural traits shared by early hominids and chimpanzees. However, it is not these cultural traits that are of the most interest; rather it is presumed shared patterns of aggression between chimps and humans. The authors of Demonic Males claim that only two animal species—chimpanzees and humans—live in patrilineal, male-bonded communities that exhibit intense territorial aggression, including lethal raids that seek vulnerable enemies to kill. Wrangham asks:

Does this mean chimpanzees are naturally violent? Ten years ago it wasn't clear. ... In this cultural species it may turn out that one of the least variable of all chimpanzee behaviors is the intense competition between males, the violent aggression they use against strangers, and their willingness to maim and kill those that frustrate their goals. ... As the picture of chimpanzee society settles into focus, it now includes infanticide, rape, and regular battering of females by males.27

Since chimpanzees and humans share these violent urges, the demonic male paradigm emphasizes that chimpanzees and humans also share an inborn morality. Those long evolutionary roots of blood lust, those aggressive urges, those Dostoevskian demons, rise out of a 6-million-year-old curse we share with our closest kin! We are apes of nature!

Whoa! Let's calm down for a moment and look at a few details before we proceed any further with demon chimps and devil humans. Certainly humans hunt, and chimpanzees are also hunters who have specific predatory strategies in specific geographic populations—different cultural approaches, so to speak. But humans and chimpanzees are not the only primates that hunt for food. Some prosimians (certain lemurs, lorises, and tarsiers) are highly insectivorous, and many catch and eat small snakes, lizards, and amphibians. Neither are humans and chimpanzees the only primate hunters of mammals. The baboons of Africa and the capuchin monkeys of South America are hunters of small mammals. And chimpanzees and humans are not the only "higher" apes who hunt. Chimpanzees are the most carnivorous of our close relatives, but orangutans have been observed out on successful hunting forays, as have bonobos and gibbons.

Humans and chimpanzees are not even the only primates that hunt and eat other primates! Orangutans prey on lorises and gibbons; baboons eat bushbabies and vervet monkeys; blue monkeys prey on bushbabies; capuchin monkeys prey on titi monkeys and owl monkeys; red ruffed lemurs prey on infant ringtailed lemurs; and dwarf lemurs have been observed hunting and eating smaller mouse lemurs.28

But, only a few instances of primates preying on other primates are relatively well studied, and the emphasis has been on chimpanzee predation. At Gombe National Park in Tanzania, chimpanzee predation on red colobus is extensive, alleged to result in the death of a minimum of one-sixth to a maximum of one-third of the red colobus monkey population every year since the study began. (We won't even deal with the fact that if the higher end of this killing rate went on for long, there would, eventually, be no more red colobus monkeys.) There are other locations where chimpanzees also prey on red colobus monkeys (chimpanzees, for the record, have been seen preying on twenty different primate species), but not at the heavy rate observed in Gombe. Christophe Boesch, who with his wife Hedwige has researched chimpanzees in the West African nation of Côte d'Ivoire, believes that human presence had a much stronger impact on chimpanzee hunting of red colobus in Gombe than in the Tai Forest where Christophe and Hedwige's investigations take place. Nonetheless, the Boesches have identified red colobus as the most significant prey item for chimpanzees in the Tai Forest.29

So, there seems to be no doubt that many primate species will eat meat and hunt for meat—sometimes opportunistically, sometimes with purposeful intent. Where we differ from Wrangham and Peterson, Craig Stanford, and Michael Ghiglieri (and Raymond Dart, Sherwood

Bonobo Eating Meat

The bonobo, one of our closest relatives, has been used as an example of an ape that "lost" the desire to hunt and kill. (N. Rowe)

Washburn, and E. O. Wilson before them) is the theory that killing and violence are inherited from our ancient relatives. And we further disagree with their argument that killing and violence are traits shared by hominids and chimpanzees not as by-products of hunting, but rather the inverse: it is this violent nature and natural blood lust (say the sociobiol-ogists) that makes both humans and chimpanzees such good hunters.

The bonobo (the "gentle" pygmy chimpanzee) helps them to this conclusion. Sociobiologists claim that bonobos have lost the desire to kill, as well as losing the desire to hunt; that they have suppressed both personal and predatory aggression; that even though bonobos evolved from a chimpanzee-like ancestor who was both a hunter of monkeys and a hunter of its own kind, during the evolution of bonobos the males lost the desire to kill each other and the desire to kill prey; and finally, that bonobos and chimps tell us murder and hunting are very similar.

Wrangham believes that blood lust ties killing and hunting tightly together, but in his scenario it is the desire to kill that drives the ability to hunt. Like other sociobiologists, he believes this lust to kill is based upon the selfish gene.

The selfish gene is an "elegant" sociobiological theory made popular by Richard Dawkins in his book of the same name.30 (Scientists use the word elegant to describe theories that explain complex natural phenomena in a very polished and minimalistic style.) Dawkins' theory is so elegant that it has been accepted, incorporated, and has now reached the level of conventional wisdom in biology. Dawkins' selfish gene explains animal behavior in truly elegant style because it provides an umbrella explanation for every single thing that animals do—all behavior serves selfish ends. The selfish gene theory can be used to explain why humans that hated and killed their enemies were survivors. Natural selection would favor those that killed over those that might hesitate and be killed.

The selfish gene theory is also used to explain why bonobos don't kill their enemies. Is this level of generality elegant or hopelessly simplistic? To us it has about the same explanatory power as that of the eighteenth-century philosopher Jeremy Bentham's "moral philosophy," which claimed that human behavior is governed solely by pleasure and pain. Bentham believed that all behavior is dictated by seeking to enhance pleasure and to minimize the likelihood of pain. Both the selfish gene and Bentham's moral philosophy attempt to explain everything—and therefore explain almost nothing.

As with many of the sociobiological theories, we find problems with both the theory itself and with the evidence used to support it. The book Demonic Males states that humans and chimpanzees might share biologically fixed behaviors based on two assumptions: First, humans and chimps are more closely related to each other than chimps are to gorillas; secondly, chimps are a good model for our earliest ancestor and retain so-called conservative (conservative in the biological context basically means "relatively unchanged by recent evolution") traits shared by both.

The first of these statements is still a hotly debated topic because the chimps, gorillas, and humans are so close genetically that it is difficult to tell exact divergence times or patterns between the three.31 The second statement is just not true. Chimpanzees have been evolving for as long as humans and gorillas, and there is no reason to believe that ancestral chimps were highly similar to present-day chimps. The fossil evidence is extremely sparse for the great apes. It is likely that many forms of apes have become extinct during millions of years—just as many forms of hominids have become extinct. Furthermore, even if chimpanzees were a good model for the ancestor to chimpanzees and humans and a "conservative" representative of this particular branch of the evolutionary bush, it would not follow that humans would necessarily share specific behavioral traits. As the authors of Demonic Males emphasize, chimps, gorillas, and bonobos are all very different from one another in their behavior and in their willingness to kill others of their species. It is exactly because of these differences, in fact, that the authors agree that conservative retention of traits alone cannot explain the drastic behavioral similarities and differences.

Let's examine the "proof" of Wrangham and Peterson's theory that, we must reiterate, doesn't rest on theoretical grounds but depends solely on the circumstantial evidence that violence and killing in chimpanzees and humans are behaviors that are similar in pattern, have ancient shared evolutionary roots, and are inherited. Humans and chimpanzees kill members of neighboring groups of their own species—we can't argue that this happens, particularly with humans. This is a startling exception to the norm for animals—actually, there are many exceptions, such as lions, wolves, spotted hyenas, and a number of other predators. Fighting adults of almost all species normally stop at winning: They don't go on to kill—the fact is that most species do not have the weapons to kill one another as adults. Aggressive, unfriendly behavior between adults of many species is common in various circumstances,32 but certainly it would take two adult squirrels, rabbits, or aardvarks much more energy than it is worth to kill their opponent rather than to drive it away. They just don't have the tools. Chimpanzees and humans do, although the tools they use are radically different.

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  • iivari
    Why are humans and chimpanzees the only primates to eat meat?
    8 years ago
  • nelly
    What would happen if chimpanzees become extinct?
    3 years ago

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