A skull discovered deep in a cave system in northern Spain, known as cranium 17, is the oldest known forensic murder case in the human lineage, dating back roughly 430,000 years. The fossil shows two deliberate, measured impacts above the left eye of a young adult, inflicted from slightly different angles by the same blunt object. The victim was not killed by a fall or an animal attack but was struck by someone facing them, then dragged to a 13-meter vertical shaft and dropped into the darkness. The analysis, published by Nohemi Sala and Juan Luis Arsuaga in PLOS ONE in 2015, raises a profound question: did humans invent violence, or was it already written into us long before we had a word for it?
Evidence from our closest living relatives suggests the capacity for violence predates humanity. In 1974, Jane Goodall observed a chimpanzee community at Gombe Stream National Park in Tanzania split into two groups. Over four years, the northern Kasakela males systematically hunted down and killed every male in the southern Kahama group, one by one. The first attack, on January 7, 1974, saw six males ambush a lone individual named Godi and beat him for over ten minutes.
By 1978, the Kahama community no longer existed. Goodall, who had believed chimpanzees were essentially peaceful, was forced to revise her understanding of primate behavior. This pattern is not isolated to one community. A 2014 analysis led by Michael Wilson, compiled from 18 chimpanzee and four bonobo communities across five decades, documented 152 lethal attacks.
The vast majority of attackers were male, and most victims were rival males or infants. Crucially, the killing rate was not linked to human disturbance but to population density and competition between males, indicating the violence arose from within the animals’ own social dynamics. Bonobos, who are equally closely related to humans, show far lower rates of lethal violence, but they still retain the capacity for aggression, suggesting the difference is ecological and social rather than a complete absence of the trait. Researchers have attempted to quantify the inheritance.
A 2016 study led by José María Gómez in Nature compiled data on over four million deaths across more than 1,000 mammal species. While the average mammalian baseline for lethal violence was about 0. 3 percent, the rate among primates was roughly 2. 3 percent.
Modeling predicted that the ancestral rate for the human lineage was approximately 2 percent, or one in fifty deaths. This suggests lethal aggression is not a cultural invention but a phylogenetic inheritance from a line of social, territorial primates. The neural and biological hardware for aggression is also deeply embedded. The circuitry runs from the amygdala, the brain’s threat detection hub, through the hypothalamus, which acts as an activation switch.
A 2011 study in Nature from David Anderson’s laboratory at Caltech showed that stimulating a specific cluster of neurons in the ventromedial hypothalamus of mice instantly triggered attack behavior. Sitting above this hardware is the prefrontal cortex, which acts as a brake by evaluating consequences and suppressing impulses. The famous case of Phineas Gage, whose left frontal lobe was pierced by an iron rod in 1848, demonstrated that damage to this region leads to impulsive aggression. A 1994 reanalysis of his skull confirmed the injury was centered on the ventromedial prefrontal cortex.
Genetics also play a role, but in complex ways. In 1993, a study identified a mutation in the MAOA gene in a Dutch family that caused severe impulsive aggression in fourteen males. This became known as Brunner syndrome. However, a landmark 2002 study in Science found that a common low-activity variant of this gene, sometimes misleadingly called the warrior gene, did not predict violence on its own.
It only increased the risk of antisocial behavior in boys who had suffered severe childhood maltreatment. The gene loaded the gun, but the environment pulled the trigger. The poorly named label fails to account for populations where this variant is common yet violent crime rates are low. Testosterone is similarly misunderstood.
It does not generate aggression from nothing. According to neuroendocrinologist Robert Sapolsky, it operates through a permissive effect, lowering the threshold for status-seeking behavior. In contexts where status is gained through aggression, testosterone amplifies aggression; in contexts where status is gained through cooperation, it amplifies cooperation. A 2010 study in Nature found that women who received testosterone made fairer offers in an economic game, while women who merely believed they had received it acted more aggressively.
Paradoxically, humans are also the most docile primates in everyday social settings. Chimpanzees physically intimidate each other at rates vastly higher than humans do. We share trains, stand in lines, and trust strangers. Richard Wrangham, in his 2019 book The Goodness Paradox, argues that humans domesticated ourselves, and the mechanism was execution.
Weapons and language allowed subordinate males to coordinate against dominant bullies. Across hunter-gatherer societies, overly aggressive individuals were monitored, ostracized, and in extreme cases killed by a coalition of the group. Repeating this over hundreds of thousands of years created artificial selection, suppressing the hot, impulsive reactive aggression while leaving the cold, calculated proactive aggression intact. The bully became rare; the war council became universal.
The archaeological record traces the escalation of lethal technology. In 1994, nine wooden spears dating back roughly 300,000 years were found in Germany, carved by Homo heidelbergensis. They were precision throwing instruments, with their center of gravity positioned like modern Olympic javelins, designed for coordinated big-game hunting. By 3,300 BC, a man known as Ötzi was shot in the back with a flint-tipped arrow, bleeding to death within minutes.
He had suffered a knife wound days earlier, suggesting he had survived one fight, fled into the mountains, and was hunted down. The oldest evidence of chronic intergroup violence comes from Jebel Sahaba in Sudan, dating to roughly 13,000 to 14,000 years ago. A reanalysis published in 2021 examined all 61 skeletons and found that two-thirds showed violent trauma, including embedded projectile points and healed wounds from previous attacks. Around the same period or shortly after, at Nataruk in Kenya, researchers found the remains of 27 people, including a bound pregnant woman, left where they fell in the mud.
This massacre, around 10,000 years old, involved attackers who traveled with obsidian weapons from outside the local area, indicating a planned raid. Mass graves from later periods, in Germany and South Dakota, show similar patterns of total destruction, with families wiped out and, in some cases, young women abducted. Statistical comparisons reveal how different the scale of this violence was. Lawrence Keeley’s 1996 book War Before Civilization calculated that tribal societies suffered roughly 500 war deaths per 100,000 people annually, compared to about 15 per 100,000 for the United States in the 20th century.
Samuel Bowles estimated in a 2009 paper that intergroup warfare accounted for roughly 14 percent of all adult deaths in pre-state societies. This constant external threat is what he argues drove the genetic evolution of parochial altruism, the willingness to die for your group. The rise of the state changed the equation. Thomas Hobbes argued in 1651 that life without centralized government was a war of all against all.
The state, as Max Weber later defined it, claims a monopoly on the legitimate use of physical force. Criminological data suggests this shift mattered. In medieval Oxford, the homicide rate was roughly 110 per 100,000 per year; by the 20th century, it had fallen below one. Steven Pinker argued in The Better Angels of Our Nature that this decline, driven by centralized states, trade, and expanding empathy, is a long-term historical trend.
However, critics note that war deaths follow a power-law distribution, meaning the catastrophic outliers like the world wars are so extreme that the historical average understates the actual risk. The 20th century killed between 150 and 200 million people through war and state-sponsored mass murder. So, did humans invent violence? The answer is both no and yes.
The capacity for lethal aggression is a primate inheritance, present in our neural circuitry and our lineage. The oldest murder case is 430,000 years old and likely was not the first. But warfare, the organized, premeditated, large-scale application of lethal force by one group against another, is an invention. It required preconditions that did not exist for most of human history: settled communities, stored surplus, territory worth defending, and populations too large for personal relationships to manage conflict.
It was not inevitable in its specific forms, but it was probable. In 1986, the Seville Statement on Violence, later adopted by UNESCO, concluded that biology does not condemn humanity to war. The same species that invented the spear invented the treaty. The same brain that houses the amygdala houses the prefrontal cortex.
The capacity for violence is inherited, but so is the capacity for cooperation. What humans have developed, slowly and imperfectly, is not the invention of violence, but the invention of hesitation, the fraction of a second where the ancient impulse fires and a different decision is made. Whether that invention holds is constantly being tested.