Why societies experience cycles of violence and peace

Archeological evidence shows bloodshed waxes and wanes, influenced by climate and other factors.
An ancient brown skull with a metal arrowhead protruding from its side.
A human skull found in the Tollense valley, an ancient battlefield in Germany, with fatal trauma caused by a Bronze arrowhead. Volker Minkus

Is human society becoming more violent? It’s hard to imagine a point in time containing an event as destructive as an atomic bombing. Even the most brutal acts committed by our ancient ancestors pale in comparison to the organized assaults countries have executed in the last century alone. Ongoing wars and human right violations suggest that we are living in one of the most vicious times in history. But the evidence, according to archaeologists who study historical violence, says there is no black-and-white answer.

To conclude that humans are more violent than ever, you’d need a timeline of all the aggressive actions in human history. Archaeologists have found some artifacts that weave a story of humanity’s violent past from a skeleton that could have been the first murder victim about 430,000 years ago to the ancient Mesopotamian death pits that likely held war casualties or human sacrifices. These pieces of history, though, are still not enough to paint a complete picture. 

The further we go back in time, the harder it is to assess violence and killings, explains Linda Fibiger, an archaeologist at the University of Edinburgh in the United Kingdom, who researches conflict in early human history. 

Remains alone don’t tell complete stories. Finding enough evidence to know whether humans at a certain time period were violent, or if someone’s violent death was an isolated event, is tricky. Even if an autopsy of an ancient human implies a brutal death, it can’t reveal a killer’s motive. Some ceremonial acts, for example, were interlaced with violence as people were sacrificed as tributes to the gods.

[Related: Grisly medieval murders detailed in new interactive maps]

“I don’t think prehistory was in an eternal state of warfare and conflict. But with the skeletal evidence and the percentage of individuals with violent trauma, I’m sure most people would have been aware of violence or known somebody who encountered it,” says Fibiger. She also notes whether people in the past considered an act a crime could change the perception of whether they were living in a violent time.

If perception is a factor, it’s possible we could be living in the most peaceful era to date. In his 2011 book The Better Angels of Our Nature: Why Violence Has Declined, cognitive psychologist Steven Pinker theorized that small hunter-gatherer groups were the most violent, back in the day, with the highest percentage of people dying from warfare. As communities settled into more organized states, they were better able to become more “civilized” and develop skills of empathy, reasoning, and self-control.

“We would like to believe that we’re so much more smart, reasonable, and more civilized”, says Dean Falk, an evolutionary anthropologist from Florida State University. “But I don’t think everything’s peachy now.” Falk, in her previous analysis of the evidence Pinker presented, found that he failed to consider the population sizes of the different communities in his calculations. This could have inflated the rate of war deaths in hunter-gatherer communities when comparing them to state-based societies. And although a larger percentage of a small society may have died in a conflict, Falk argues that says more about the attacks they suffered than their own violent behavior.

When Falk included the absolute number of deaths (the number of deaths for a given population scaled to their size) into the calculations, she found it was the population size, not the type of civilization structure, that determined whether a society lost their residents to warfare. And while the percentage of annual war deaths was lower among state societies, Falk says the number of annual war deaths has gone up in bigger populations. “This might have to do with big brains and having technology to invent more effective weapons to kill each other.”

There’s also no rule that states we’re on a linear path toward a more or less violent society. New research published this month in the journal Nature Human Behaviour suggests human violence has waxed and waned throughout history. Giacomo Benati, an archaeologist at the University of Barcelona in Spain and coauthor of the new study says analyzing violent trends across history often falls victim to bias, focusing on historical battle records or polarized narratives of the ancient world. 

[Related: A group of humpback whales is choosing violence]

His new work, one of the largest archaeological studies on early human violence, tries to avoid that prejudice, by examining  a large set of bones. Benati and his team analyzed any sign of cranial trauma or weapon-related wounds in 3,539 skeletons belonging to people who lived in seven Middle Eastern countries between 12,000 to 400 BCE. 

This study was particularly interesting because it tries to contextualize what’s happening, says Fibiger, who was not involved in the research. The large dataset of human skeletal remains allowed them to link traumatic deaths to ongoing conflicts, economics, and the unequal distribution of resources and wealth caused by climate. “Bringing these things together gives a better concept of people’s lives,” Fibiger says, “and what might have escalated conflict and broken down relationships.”

Interpersonal violence—murder, torture, slavery, and other cruel punishments—peaked around 4,500 to 3,300 BCE during the Chalocolithic period, Benati and his co-authors concluded. The high rates of violence could have to do with the formation of political units vying for control, which may have escalated local quarrels to larger and more organized conflicts.

Benati says the most surprising finding was the steady drop in violence across the Early and Middle Bronze period, which he suspects has to do with better living standards. “After going through thousands of photos of excavated skeletons, life before modern medicine [did] not look pretty,” he says. “It was short, and they had to live with constant ailments and pains.”

Violence rates appeared to pick up again through the Late Bronze Age and Iron Age. People may have become more violent due to a drier climate. The Iron Age ushered in a 300-year drought which contributed to crop shortages and widespread famine. This lack of water would have stressed out communities, leading to competition over resources. This possessiveness for limited resources—whether land or food—are universal motivators for violence that is still seen today, Fibiger points out. Additionally, given the worsening climate situation right now, Benati says how people reacted to extreme climate events in the past could tell us how people will react to instability in the future. Climate change, for example, may once again herald a longer period of violence. 

Given our bloody record for handling conflict, archaeologists remain divided on whether humans will ever live in a violent-free society. Fibiger believes people are not inherently violent, but may be pushed into situations where they are required to defend themselves or their livelihood. By learning from violence in the past, she believes humans can do better. Falk is less optimistic. She says it’s possible we will wipe out our species, seeing that we are just as capable of violence as our ancient ancestors. The only difference now is our access to more lethal weapons and more organized warfare. “For proof of that, just turn on your TV to the evening news.”