This is from my upcoming book, Indivisible, beginning on page 113.

Is it in our genes?

My exploration didn’t stop with social science. Some people suggest that violence is truly biological, present in us from birth, a way of asserting our will and controlling our environment. Others suggest that violence is a result of environmental factors. We used to debate whether it was nature or nurture that determined who we became and how we acted; now we know it is always both.

I began to think of this using a technology metaphor: If nature is the genetic mainframe we are born into, the hardware or the operating system our bodies run, then nurture is our programming.
There is a clear and constant interaction between genes and environment, as our environment determines which genes are called on to express themselves in daily encounters, to direct our actions. We are who we are, but we are also who we become, due to this critical interplay between genetic hardwiring and our environmental programming.
What if our disconnections, alienations, and the violence we do to one another is not biological, but a flaw in our cultural programming, our “code?” If that is the case, the intersections of biology and psychology and environment that produce disconnection and violence can be retrained.
So what does the research say?
It says, in part, that yes, there appear to be specific genetic markers for violent behavior. Guang Guo at UNC Chapel Hill has identified “three genes that play a strong role in determining why some young men raised in rough neighborhoods or deprived families become violent criminals, while others do not. Guo found specific variations in three genes that were associated with bad behavior, but only when the boys suffered other complex environmental stresses.”
So it is true that some people, when confronted with difficulty, seem to be programmed, biologically, to be violent. Conversely, those who don’t have these markers will respond to the same situation without violence. But that is not the full story, because many people who have these markers never express them—because they have never been placed into a situation where the genes have been triggered. Some are placed into those situations, but don’t become violent due to support systems and training. There are also people who have these genes do behave violently, because they have been in violent and abusive circumstances.
The genetic markers for bad behavior are triggered by complex stressors and bad environments; that is to say, extreme violence can sometimes be a genetically amplified reaction to bad environments.
But what is a “bad environment?” That too, it turns out, has been studied. The strong predictors of violent expression are very specific kinds of poor parenting (regardless of socioeconomic status), with an emphasis on the following characteristics: “poor supervision; erratic, harsh discipline; parental disharmony; rejection of the child; and limited involvement in the child’s activities.” The second predictor is exposure to first-hand violence, and the third is exposure to media violence.
Researcher Bruce Perry states that “the most dangerous children are created by a malignant combination of experiences. Developmental neglect and traumatic stress during childhood create violent, remorseless children.”
Kids with neglect and trauma have highly sensitized and poorly regulated brainstem systems, which results in a whole list of problems (anxiety, impulsivity, poor affect regulation, motor hyperactivity, low empathy, impaired problem-solving skills). Chaotic home environments and under-socialized development predispose these kids to all kinds of neuropsychiatric challenges and to violent behavior.
These kids have lost the neural circuitry needed to regulate their emotions. Richard Davidson says, “Normal individuals are able to voluntarily regulate their negative affect and can also profit from restraint-producing cues in their environment, such as facial and vocal signs of anger or fear, that also serve a regulatory role. Individuals predisposed to aggression and violence have developed abnormalities in the central circuitry responsible for these adaptive behavioral strategies.”
For the component that is genetic, violent natures can be amplified by transgenerational selection. In violent societies, that is to say, there are more people with these genetic markers than nature would have on balance. It’s a passive form of selective breeding.
Here is an example of how selective breeding works in the animal kingdom: In Russia, there is an ongoing experiment in which foxes have been bred for 20 generations. The breeders select the sweetest in the litter, and they also pick the most violently disposed, and then breed those animals separately. After 20 generations, the sweetest foxes were smart, kind house pets, and the violent foxes were so fierce that trainers could not approach their cages without the foxes trying to attack.
So there are a lot of damaged people out there who are now doing damage to others, often part of a multiple generation problem, perpetuating the –cycle. What do we do?

–End of Excerpt–