by Joe Kenda says extreme violence lives in everyone’s DNA, waiting for emotion to overrule judgment. My friend is a great detective and a shaky geneticist, and the difference matters. Janna and I have known Lt. Joe Kenda the way friendships form now, across screens and wires, built from years of mutual attention. It began when he found this blog more than a decade ago and, in the phrase that gave an old post its title, stayed followed. He has sent us gifts. He is, in the way that counts, a generous man, courteous to strangers who admire his work and himself in a business that rewards performance. So when he stood at CrimeCon and told a room full of true-crime devotees that every person in it carried a ball of violence encoded in their genes, I listened closely. Then I did the thing you owe a friend whose mind you respect. I checked whether it was true.
Here is what he said:
“Humans have a condition formed by DNA throughout the millennia. We’re all afraid of fire. We’re all afraid of animals that are aggressive. It’s in your DNA. But there’s something else in your DNA. It’s a ball of violence. Extreme violence is in all of us. Me and every one of you. It requires the motivation for your emotion to overcome that judgment and set that ball of violence in motion. And most of you will carry on your entire lives and never have that move a centimeter. Others will not. Their emotion will overcome their judgment. And they will engage in extreme violence. Absolutely extreme violence. I’ve seen death by every means except a nuclear weapon. I’ve never seen that. But I’ve seen impressive extreme violence cases where we weren’t sure if the victim was a man or a woman because they were so disfigured. So it’s in all of us. And everyone is capable. And fortunately, not everyone does it. But many do. People you’d never suspect of doing it, but do it anyway.”
A man who worked homicide for twenty-three years and cleared his cases at a rate most detectives never approach has earned the right to a theory of human darkness. The question is whether the theory holds. It holds in one place and fails in another, and the two places are worth separating, because the part Kenda gets right is the part most people refuse to hear, and the part he gets wrong is the part that sounds most like science.
Strip the rhetoric and he makes four separate claims, which do not stand or fall together. First, that certain fears are wired into us by evolution, fire and dangerous animals among them. Second, that a comparable inheritance of extreme violence sits in every human genome. Third, that this violence stays dormant until emotion overpowers judgment. Fourth, that anyone can cross the line, including the neighbor no one suspects. His first claim is partly right and partly folklore. Number two is where the argument strains hardest against the evidence. Claims three and four carry more truth than comfortable people want to admit, though for reasons Kenda misidentifies.
The fears come first, because they set up everything else. Some human fears do arrive pre-loaded. Susan Mineka’s laboratory monkeys, raised without ever meeting a snake, learned to fear snakes faster than they learned to fear flowers or rabbits when they watched other monkeys react with alarm. Arne Öhman found the same bias in people: we acquire fear of snakes and spiders and heights more readily than fear of cars or electrical outlets, though the second set kills far more of us. Evolution left us primed for the dangers of the deep past. Fire, though, is the weak leg of Kenda’s example. Children are drawn to flame, not repelled by it, which is why every parent spends years saying no. Our species has tended fire for hundreds of thousands of years and cooks its food over it. The fear we feel near a burning house is mostly learned, taught by heat and by warning. Kenda reached for the most familiar example and picked the one with the least support behind it, which tells you he is reasoning from a detective’s intuition, and intuition can run ahead of what the record can show.
The Pedigree of a Dark Idea
The belief that violence lives inside us, coiled and waiting, is older than any science that could test it. Augustine built a theology on it, naming the inheritance original sin and locating the fault in a will bent toward wrong from birth. Thomas Hobbes gave it political form in 1651, describing a state of nature as a war of all against all, where life ran solitary, poor, nasty, brutish, and short, and only an absolute sovereign could keep the knives down. Jean-Jacques Rousseau spent a career arguing the reverse, that people come into the world decent and are spoiled by property, envy, and the societies they build. The quarrel between those two men, the beast restrained against the innocent corrupted, is the same quarrel we are still holding over Kenda’s ball of violence.
Sigmund Freud sided with Hobbes and gave the dark view its modern vocabulary. In his 1930 essay on civilization and its discontents, and in the letter he wrote Einstein two years later under the title Why War, Freud proposed a death drive, an aggressive instinct as basic as the drive toward love, and argued that culture exists mostly to dam it. Konrad Lorenz, the Austrian ethologist, carried the idea into biology with his 1966 book On Aggression, picturing aggression as a fluid that accumulates in the organism and must periodically discharge, like water rising behind a wall. If that image sounds familiar, it should. Kenda’s ball of violence, held in check until emotion sets it in motion, is Lorenz’s hydraulic model in street clothes.
The most theatrical version came from a playwright. Robert Ardrey, who wrote for the stage before he wrote about human origins, published African Genesis in 1961 and sold millions on the thesis that we descend from a killer ape, that Raymond Dart’s fossil hominids had been murderers with weapons, and that our talent for slaughter is the engine of our success. A dramatist gave us the killer-ape story, which should interest anyone who works in both fields, because the story is superb theater and shaky anthropology. Its bones are still rattling around in statements like the one Kenda made at CrimeCon.
I trace this lineage to locate Kenda inside it, because knowing where an idea comes from tells you which objections it has already survived and which it has not. When Kenda says extreme violence is in your DNA, he is speaking a hundred-year-old tradition that runs Augustine to Hobbes to Freud to Lorenz to Ardrey, and that tradition met serious resistance for good reasons. In 1986 a group of twenty scientists from a dozen countries met in Seville and issued a statement, later adopted by UNESCO, rejecting as scientifically unsound the claim that humans have inherited a tendency to make war, that violence is programmed into our nature, or that a single instinct drives it. They were answering the Lorenz and Ardrey picture directly. The statement was itself contested, and some called it politics dressed as science, yet it marked the moment the field stopped treating innate bloodlust as settled fact.
Where Kenda Is Right
Now the uncomfortable part, the part that makes Kenda worth arguing with rather than merely correcting. On the claim that upsets people most, that anyone is capable and that the killer is often the person you would never suspect, the evidence sits largely on his side.
Stanley Milgram ran the experiment that should end the comfortable view. At Yale in the early 1960s he told ordinary volunteers to deliver electric shocks to a stranger, raising the voltage each time the stranger answered wrong. The stranger, an actor, screamed, begged, complained of a heart condition, and fell silent. Roughly two-thirds of the volunteers went all the way to the final switch, marked with a lethal charge, because a man in a lab coat calmly told them to continue. None of them had been recruited for cruelty. They were New Haven residents who answered a newspaper ad, and most of them sweated and protested and obeyed anyway. Later scholars have picked at Milgram’s methods and questioned how he ran the sessions, and they are right to, yet gentler re-creations decades on still find ordinary people willing to go frighteningly far on instruction.
Then read Christopher Browning’s Ordinary Men, the study that should be required for anyone who believes evil wears an obvious face. Browning reconstructed the record of Reserve Police Battalion 101, a unit of roughly five hundred middle-aged German men, mostly working-class Hamburgers, too old for the army, many not even party members. In 1942 they were ordered to shoot Jewish civilians in Poland at close range, and their commander offered anyone who could not face it the chance to step out. Almost none did. Over the following months these unremarkable men shot tens of thousands of people, and Browning’s grim finding is that conformity, deference, and the pressure not to look weak in front of comrades were enough to turn mailmen and shopkeepers into mass murderers. Daniel Goldhagen later argued they killed because German culture had bred them into willing exterminators, a narrower and more comforting story for the rest of us. Browning’s version is worse, and better supported, because it implicates the species rather than one nation.
Kenda’s own casework points the same direction, and here his witness is real. Most homicide happens between people who know each other, in kitchens and bedrooms and driveways, over money and jealousy and a bad night that went past the point of return. The spouse, the son, the mild neighbor, the man everyone described afterward as quiet and kind: these are the ordinary faces of murder, and a detective sees them for decades. When Kenda says people you would never suspect do it anyway, he is reporting twenty-three years of data from the one place in society where the base rate of killing runs high enough to study up close.
The deep history supports the capacity too. Jane Goodall watched the chimpanzees of Gombe wage what she could only call a war, one community systematically hunting down and killing the males of a splinter group over four years. Richard Wrangham built a career on that observation, showing that lethal, planned, coalitionary violence, males banding together to kill vulnerable rivals, appears in chimpanzees and in humans and in almost no other animal. Behavioral genetics adds a layer. Twin and adoption studies converge on the finding that roughly half the variation in aggressive and antisocial behavior tracks with heredity. There is a biology of violence, and Kenda is right that it is old, shared, and written partly in our genes.
Where the DNA Story Breaks
Here is where I have to disagree with my friend, and disagree hard, because the sentence that sounds most scientific is the one the science does not support. There is no ball of violence sitting in every genome, loaded and waiting for a spike of emotion to fire it. That picture gets the mechanism wrong, and the errors compound.
The gene everyone points to is MAOA, nicknamed the warrior gene, which breaks down neurotransmitters in the brain. A low-activity version has been linked to aggression ever since Hans Brunner described a Dutch family in 1993 whose men carried a broken copy and showed a pattern of impulsive violence. If genes loaded a violence ball, this would be the ammunition. Then in 2002 Avshalom Caspi and Terrie Moffitt published the study that changed the conversation. They followed a large group of boys into adulthood and found that the low-activity MAOA variant predicted violent, antisocial behavior almost entirely among men who had been abused as children. The same gene in men raised without maltreatment predicted almost nothing. The gene did nothing on its own. It set a trap that only a brutal childhood could spring.
The neuroscientist James Fallon made the point on himself by accident. Studying the brain scans of murderers, he found the pattern that marks the psychopathic killer, low activity in the regions that govern empathy and restraint, and then discovered, comparing scans in his own lab, that one of the murderer-pattern brains was his own. He carried the warrior-gene variant too. Fallon has spent his life as a productive scientist who has never killed anyone, and his own explanation is a happy, secure childhood. Genetics dealt him the hand Kenda describes and it never became violence, because the trigger Kenda names, emotion overwhelming judgment, matters far less than the environment that shapes whether the judgment forms at all.
None of this denies a biology of violence. Adrian Raine’s brain scans of murderers show measurable differences in the regions that govern impulse and empathy, and the twin studies are real. What that research describes is variation between people, some carrying more risk and some less, which is the opposite of a uniform ball issued to everyone at conception. Heritability of roughly half means that people differ, and difference is exactly what a claim of universal, identical inheritance cannot accommodate. The biology points to a spectrum of individual risk, shaped at every step by what happens to the person. It offers no species-wide detonator.
The hardest refutation comes from our nearest cousins. Chimpanzees raid and kill. Bonobos, just as closely related to us, sharing a common ancestor with chimpanzees more recently than either shares with people, settle their tensions with sex and reconciliation and almost never kill each other. Two species, nearly identical genomes, opposite dispositions toward lethal violence. If a shared primate inheritance settled the question, the two of them would behave alike. They do not, which means genes propose and ecology, social structure, and development dispose. To point at human DNA and read off a verdict of violence is to ignore the bonobo standing right beside the chimp.
Wrangham’s own work carries the sharpest irony for Kenda’s thesis. Humans, he argues, are a self-domesticated species, shaped over tens of thousands of years, in large part by our own communities executing the most aggressive men, into unusually low reactive aggression. We manage something extraordinary every day. Six hundred strangers pack into an aluminum tube at thirty-five thousand feet, share a bad meal, and land alive. Try that with chimpanzees and the plane arrives full of corpses. Our talent runs toward the cold, planned, organized violence of armies and executions and premeditated murder, while our everyday, hot-tempered, lash-out violence is unusually low for a primate. A ball of violence straining against a thin membrane of judgment describes a chimpanzee far better than it describes a human being.
Then there is the tell inside Kenda’s own words. He says that most people will go their entire lives and never move the ball a centimeter. If the ball never moves across seventy or eighty years, through every provocation, betrayal, grief, humiliation, and rage that a long life delivers, in what meaningful sense is it a loaded weapon inside them? A gun that no pressure available in an ordinary lifetime can make fire is not a gun in any useful sense. Kenda’s metaphor works against his own observation. The capacity he sees in the rare killer is real. Its supposed presence, cocked and dangerous, in the great majority who never come close, is an inference the evidence will not carry.
The Seduction of the Monster Within
There is a reason Kenda’s claim lands so well with a crowd, and the reason should make us cautious rather than convinced. The idea that anyone can become a monster feels humbling and wise. It flatters us in reverse, granting the speaker a hard-won knowledge of the abyss and the listener a shiver of self-recognition. That emotional payoff has led a great many intelligent people to believe thin evidence.
The clearest case is the Stanford Prison Experiment. For half a century, Philip Zimbardo’s 1971 study, in which college students assigned to play guards supposedly slid into cruelty within days, was taught as proof that the situation can turn any of us evil. It became one of the most cited demonstrations in psychology. Then the archives were opened. Thibault Le Texier’s examination of Zimbardo’s own tapes and papers showed the guards had been coached toward brutality, told how to behave, and pushed by the experimenters. One prisoner later admitted he faked his famous breakdown to get out and study for an exam. The experiment everyone remembers as evidence for the monster within turns out to be theater with a thumb on the scale. It survived for decades because people wanted the lesson to be true.
That is the danger with Kenda’s thesis. Its moral usefulness does not prove its mechanism. Believing that the killer could be you, or your neighbor, does real good in the world, and I will defend that use in a moment. A claim can be humane, and can even improve behavior, while being loosely argued. The warrior-gene story spent a decade in courtrooms as a supposed excuse for violence before the gene-environment research caught up and showed how little the gene decides alone. We should hold Kenda’s DNA to the standard we finally held MAOA, and admire the message without swallowing the biology.
The Detective and the Geneticist
So do I agree with him? In the way that matters most, yes. In the way he phrased it, no.
Kenda the detective is one of the better witnesses to human nature alive, and his central message is both true and needed: no one is exempt from the examination. The belief that killers are a separate species, that evil announces itself, that decent people carry no capacity for cruelty, is false, and it is dangerous, because it blinds us to the ordinary machinery of atrocity, the conformity and obedience and slow moral drift that let normal people do monstrous things. Milgram proved it in a lab. Browning found it in the archives of the Holocaust. Every homicide detective confirms it in the quiet neighbor with the shovel. If Kenda’s warning makes one listener more watchful of the pressures that could bend him, and more skeptical of the crowd telling him to do harm, it has done more practical good than a shelf of corrected genetics.
Kenda the geneticist is where I part from my friend. The ball of violence in your DNA is the old hydraulic instinct, the killer-ape reflex, the thing the field spent forty years walking back for cause. The capacity for extreme violence runs unevenly through us, not loaded identically in everyone, not kept down mainly by a thin lid of judgment. It works more like a potential, dormant in most and active in few, and what wakes it is far more often a ruined childhood, a permitting situation, a uniform and an order, or a culture that grants permission, than any reservoir bubbling in the blood. We are the strange, self-tamed ape whose everyday violence runs low and whose organized violence, when a group and a cause and a permission line up, can still be the worst thing on the planet.
That correction sharpens Kenda’s warning instead of weakening it. If violence were simply in the DNA, waiting, there would be little to do but hope your ball stays still. Because the triggers sit mostly outside us, in how children are raised and how crowds behave and what authorities demand, the warning becomes something you can act on. Watch the conditions. Guard the children. Distrust the order that asks you to hurt someone and calls it duty. The monster is rarely born and usually made, and the making is something a society can see coming and refuse.
Joe, if you read this, you followed us once and we stayed followed, and this is what it looks like when the following runs both ways. You are right that everyone should look in the mirror and see what they are capable of under the wrong sky. You are wrong about the ball in the blood. A friend who only ever nodded along would be no friend of your mind. The next round is on me, and I suspect you will enjoy the argument more than the agreement.
Leave a Reply