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Chimpanzees and the Battle Over Human Nature

Chimp peers right at you. (Photo by Michael Nichols /National Geographic Creative)
A chimp peers out from the branches of a tree, making direct eye contact with the viewer. (Photo by Michael Nichols /National Geographic Creative)

Were humans born to war?

Or is warfare a recent, rare development in our history?

A study of observations of chimpanzees earlier this year by Michael L. Wilson and others brought the fundamental questions of warfare’s origins and prevalence to the fore. As an archaeologist, I believe studies of the remains of early human civilizations have a lot to add to the debate.

Two Sides 

Scholars are divided into two schools of thought on the issue. Some (such as Choi and Bowles) argue that warfare goes back to at least the first appearance of fully modern humans 200,000 years ago. Others (such as Fry and Söderberg) suggest that warfare is a more modern, much less common phenomenon only arising under very specific conditions. Evidence in the ongoing debate consists of studies of contemporary hunter-gatherers, prehistoric cave art, and primatology.

Working in the field on an archaeological site, I am often knee-deep in the dirt, and I prefer searching for tangible evidence of what happened in the past.

Unfortunately the archaeological record is far from complete, and only a small percentage of ancient objects are preserved well enough to recover. Thus, archaeology is part CSI, part storytelling, whereby the artifacts give us only a glimpse into the mists of prehistory. It is our shared knowledge about people and culture that allows us to fill in the blanks until the next generation of archaeologists comes along with new ideas and methods, or a new discovery is made. Nevertheless, if faced with a decision to choose between direct evidence or informed guesswork, it is our responsibility to side with the facts. However, this is not always what people do.

Matt at a dig. (Photo courtesy Matthew Piscitelli)
Deep in the dirt. (Photo courtesy Matthew Piscitelli)

Of Chimps and Humans

In the study on lethal aggression in chimpanzees, the authors provide evidence that lethal coalitionary violence in chimpanzees is a result of natural selection not an inadvertent consequence of human impact.

News outlets had a field day with the story declaring that “Chimpanzees are natural born killers” and “Murder ‘comes naturally’ to chimpanzees.”

The danger of such claims lies in just how easy it is to somehow see our closest primate relatives as reflections of our past selves. In a New York Times interview, Michael L. Wilson, lead author of the seminal study, reports that by studying chimpanzee behavior “we’re trying to make inferences about human evolution.”

Unfortunately, chimpanzees (and contemporary hunter-gathers) are not an accurate reflection of our nearly 200,000 years of human history. Conditions today are entirely unlike what they have been for 99 percent of our existence. Population densities have increased exponentially, resource scarcity is an issue in many places around the globe, and no human or chimpanzee group is immune to the effects of the actions of modern nations.

If we want to better understand the origins of warfare and lethal violence we must forgo relying on analogy and instead turn to the only source of direct evidence about the past: archaeology.

While some ancient human remains show evidence of injury from armed conflict, here the damage came not at the dawn of civilization, but in recent years, when looters dug up the burials in search of artifacts to sell on the black market. (Photo by Matthew Piscitelli)
While some ancient human remains show evidence of injury from armed conflict, here the damage came not at the dawn of civilization, but in recent years, when looters dug up the burials in search of artifacts to sell on the black market. (Photo by Matthew Piscitelli)

Ask the Dirt and Bones

The most reliable way to learn about ancient warfare is to explore the human skeletal record for indications of lethal violence—projectile points embedded in bone, parry fractures (defensive wounds to the forearm), unhealed cranial wounds.

Up until very recently, no one had actually consulted these data to speculate about the history of warfare. Together with my colleague, Marc Kissel (University of Notre Dame), we’ve started the Global Skeletal Inventory—a database of human skeletal remains from across the world that we hope to transform into a Wiki-like resource for scholars to ask broad anthropological questions about health, disease, and even warfare.

We’ve already scoured the archaeological literature for human skeletal remains stretching from 200,000 years ago to around 10,000 years ago, which is when scholars agree that warfare had become prevalent.

What the Bones Say

Our research indicates that based on at least 2,900 skeletal remains of Homo sapiens recovered from over 400 archaeological sites across the globe, less than 0.1% demonstrates evidence of violence (Haas, J. & Piscitelli, M. in War, Peace, and Human Nature (ed. Fry, D. P.) 168-190 (Oxford University Press, 2013)). I find these human data from the past to be more convincing than results of a modern study on chimpanzees.

By categorizing warfare as an inevitable consequence of the human condition, our search for the origins and conditions that precipitate lethal violence (in the past or present) becomes moot. However, questioning how, why, and when warfare first started in human and even primate populations underscores the importance of understanding what leads to lethal violence in our contemporary world.

The debate over the prehistory of warfare is far from settled; until then, the battle over human nature will continue.

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