A groundbreaking ten-year study on the behavior of chimpanzees, reported in Current Biology, reveals that humanity's closest living relative expresses a propensity for human-like warfare. The nature of chimpanzee war, in which males patrol their group's territory and violently annex the territory of other groups in pursuit of land and resources, is startlingly similar to the warfare that has consistently emerged throughout human history. The study had led many to conclude that war is an innate behavior with genetic roots extending millions of years. But it may reveal more than just the genetic roots of warfare. The propensity for warfare in chimps could help explain the human conceptions of "good" and "evil" that define our laws, our social norms, and our morals.
The chimp warfare described by this study, and previously by famed primatologist Jane Goodall, includes all the behaviors that we as humans consider to be the very worst: killing, torture, cannibalism, rape, and perhaps even genocide. The adult males of a social group, which usually number about 30 to 50 in size, daily patrol the edge of their group's territory. They will often kill any male or young chimpanzees they find, sometimes eating or physically brutalizing their victims in a manner that some researchers liken to torture. In some instances, one group will "invade" and annex the territory of another, killing all but the adult females, who are forced to incorporate into the dominant group. The idea of chimp genocide may sound strange, but they are one of only three animals that has been observed wiping out entire social groups. The other two are wolves and humans. Given that humans and chimps are so closely related, and our genocidal records so pronounced, it stands to reason that this common behavior may be more than just coincidental.
Jared Diamond argues in his 1992 book, The Third Chimpanzee, that these ugly behaviors have stayed with us as our common ancestor divided into chimp and human lineages seven million years ago. What else could fully explain their constant recurrence throughout human history and across vastly different human cultures? After all, we share 97.3 percent of our genes with chimps. That common biology likely provides the genetic foundation for our shared behavior. A primatologist once told me that she refused to study chimpanzees because their remarkable humanness made her too uncomfortable and self-conscious to remain objective.
There are often valid and important reasons to go to war. But it's worth considering that humanity is ingrained with a genetic inclination that steers us, both as individual actors and as political institutions, toward warfare and worse.
But clearly humans and chimps are different. After all, we have strong moral compunctions against actions such as murder and rape, even if they remain prevalent in human society. John Mitani, the head researcher on the chimp study, explained to Time magazine:
Mitani isn't oblivious to the lesson some people might draw from the study. "Invariably, some will take this as evidence that the roots of aggression run very deep," he says, and therefore conclude that war is our evolutionary destiny. "Even if that were true," says Mitani, "we operate by a moral code that chimps don't have."
You can see this "moral code" in our formal laws as well as our informal social standards. Just like the behaviors they seek to counteract, these codes have been near universal in human societies since the Code of Hammurabi first put them into stone. Did humans evolve this moral code to repress certain behaviors and promote others? After all, the violent behaviors we find so objectionable aren't just genetically ingrained. They're also counter-productive to the functioning of large, stable social groups. As our ancestors expanded from the small, nomadic social groups of chimpanzees into large and stationary human societies, evolution would have favored individuals with the moral code we now consider universal. But evolution is a clumsy, imperfect, ongoing process. What if the transformation from violent, war-loving chimpanzee into cooperative, peace-loving human was never really complete? The tension between our inner chimp and our moral aspirations could be manifest in the most constant and universal struggle of human culture: good versus evil.
The struggle between good and evil, central to the world's major religions and ubiquitous in literature and entertainment, has preoccupied humans throughout recorded history. That sense of good and evil may be about more than a right versus wrong abstraction. The behaviors we consider to be the most evil are also the most prevalent, and in some cases the most unique, to humans and chimps. That we are genetically ingrained with a propensity for what we now consider "evil" behaviors may be exactly why we consider them evil and work so hard to construct a society to deter them. That is, we did not develop a strong sense that killing is evil just because it is morally wrong, although it certainly is. Rather, we may have such strong feeling of morality because, without them, we would revert to the "evil" behavior inherent in the 97.3 percent of us that is chimpanzee. But that does not change who we are. The Zoroastrians, ancestors of modern Iran who saw life on Earth as a constant and irresolvable struggle between good and evil, may have been more right than they could possibly have known.
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