The earliest human civilizations appeared between 3,000 and 4,000 years ago; since then, humans as a species have lived in complete peace for approximately 268 years. And according to “What Every Person Should Know About War” (Free Press, 2003), as many as 1 billion people may have died as a direct result of war.
Violence is clearly not a modern phenomenon, but is it an inherent part of being human? Have we evolved to be aggressive?
It turns out that the answer is not simple. A 2014 study published in the journal Nature (opens in new tab) noted that deadly violence was common in the communities of one of our closest living primate relatives: chimpanzees (Pan cavemen).
That suggests that violence may have been part of the human repertoire at least as far back as our last shared ancestor with chimpanzees, which would have lived about 8 million years ago.
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So it’s clear that violence has been around for as long as there have been humans, experts told Live Science.
“Violence has been an engine of much of human history,” David C. Geary (opens in new tab), a cognitive scientist and evolutionary psychologist at the University of Missouri at Columbia, told Live Science in an email. “All of mankind’s early empires were built through intimidation and violence.”
“There is also evidence of aggression before recorded history: bones with evidence of violent death, such as embedded arrowheads or skulls stabbed into them,” Beat Barclay (opens in new tab), an evolutionary psychologist at the University of Guelph in Ontario told Live Science in an email. That suggests that violence preceded complex societies and the rise of civilization.
But on the other hand, rates of violence vary wildly (and historically have varied wildly). cultures and communities, Barclay said. That suggests that violence in our species can be dramatically turned up or down.
Nomadic peoples, for exampletypically have lower levels of deadly interpersonal human violence, while eras filled with societies bent on plunder and conquest, unsurprisingly, had higher levels.
And modern times American culture is more violent (opens in new tab) than most in Europe.
“There is a wide variation in violence rates — order of magnitude difference,” Barclay noted. “In some specific recorded societies, up to half of all men die violently at the hands of other men. In other societies, physical violence is very rare, such as in modern Japan.”
Why do people become violent?
Violence often leads to violence, meaning cultures where conflict is common are more likely to experience violence generation after generation, Geary said. In this way, violence is “transmitted” as an infectious disease would be, according to University of Illinois epidemiologist Gary Slutkin (opens in new tab).
However, Brad Evans (opens in new tab), a professor of political violence at the University of Bath in the UK, pointed out that even people in the most progressive and peaceful communities are capable of violence. “Ordinary, lawful persons can quickly turn into monsters as soon as circumstances change; likewise, some who are most unpleasant can display remarkable acts of kindness. There is no clear formula for why a person acts in a violent manner. And that is why why it’s such a complex problem,” Evans told Live Science in an email.
In addition, according to both Barclay and Evans, it can be much easier to commit violent acts if the person committing the violence is far from their victims; it is much easier to press a button to launch a nuclear missile than to physically and directly deliver a fatal blow.
For example, in Stanley Milgram’s classic obedience studies, in which an experimenter told participants to administer electric shocks of increasing intensity to other people, participants were more reluctant to shock victims when they were physically closer to them, Barclay noted.
And historically, acts of Genocide takes place after perpetrators are dehumanized (opens in new tab)or create psychological distance between themselves and one’s different race or ethnicity.
Types of violence
There may also be “two types” of aggression in human evolution (opens in new tab): proactive and reactive, Richard Wrangham (opens in new tab)a research professor in the Department of Evolutionary Biology at Harvard University, reported in 2017 in the journal Proceedings of the National Academies of Science (opens in new tab). Proactive violence has historically been associated with conquest, when one group is determined to take another’s resources or land. Reactive violence, on the other hand, can be described as the immediate response to such aggression.
While violence seems to be an ingrained human trait, Barclay is confident there is room for optimism — to a point.
“Objectively, every individual today is much less likely to be a victim of violence than in previous eras,” he said. “We are currently in the most peaceful era in history. But that doesn’t guarantee it will stay that way. If we don’t fight climate change, there will be more scarcity, more disasters, more desperation and more cause for conflict.”
Originally published on Live Science.