Did humanity evolve to have psychopaths?

Psychopaths are manipulative, violent, impulsive, and lack empathy — but research suggests that psychopathy may be an evolutionary strategy rather than a disorder.

  • It's tempting to think of psychopathy as a kind of aberrant mental condition, but several studies suggest that it may be an evolutionary strategy.
  • A study compared the genetic profiles of psychopaths with individuals who were more likely to have children younger and more frequently and found significant overlap.
  • This suggests that the qualities that bring about psychopathy are also qualities that encourage more frequent reproduction, making psychopathy an advantageous strategy.

From an evolutionary perspective, it seems odd that we would have psychopaths among our numbers at all. A great deal of what's made humanity a successful species is our social cohesiveness, our empathy toward one another, and our understanding of right and wrong. What benefit could there be for individuals to simply lack these socially binding qualities and to feel a tendency toward violence to boot? The evolutionary role of psychopaths becomes even stranger when you consider the fact that psychopaths are at higher risk for becoming disabled or dying early owing to their impulsivity and reckless behavior.

It's tempting to say that psychopathy is simply the result of a short circuit in the complicated wiring that makes up our brains. However, it may be the case that psychopaths are simply employing a different reproductive strategy than the rest of us. At least, that's what Jorim Tielbeek and colleagues argue.

Looking at the genome

While psychopathy is believed to have some environmental causes, much of what brings it about is genetic. We know that there are certain mutations that encourage psychopathic personalities. Tielbeek and colleagues were curious as to whether these mutations also conferred some other kind of benefit. So, they looked at two large databases containing genotypic data on over 31,000 individuals. A prior study had also uncovered the genetic profiles of individuals who were more likely to have children younger and to have more children overall. By looking at the overlap of these two genetic profiles, the research team was able to see whether there was any correlation between the two sets.

They found that there was, indeed, a fairly significant overlap. The genes associated with having children earlier and more often are also associated with the genes that give psychopaths the characteristics that make them psychopathic, like a lack of empathy.

Why psychopathy exists

Photo by Jesús Rocha on Unsplash

It seems counterintuitive, but this finding fits well with what we understand about psychopaths. Previous research has found that psychopaths are often superficially charming, which enables them to attract others in the short term. In the long term, though, this façade crumbles over time. Psychopaths are also prone to greater disinhibition than others, meaning they have problems with impulse control and tend to seek immediate gratification. Combined, these traits would make psychopaths sexually promiscuous, and their disregard for social norms makes them more prone to poaching others' mates or sexual assault, a theory that has been supported by a number of other studies.

But if psychopathy can be a way to have more offspring, why aren't there more psychopaths? After all, Tielbeek and his colleagues' study showed that psychopaths are more likely to have more children, and we know that there is a significant genetic component in psychopathy. Wouldn't the psychopathic gene out-reproduce the non-psychopathic gene?

Why we aren't all psychopaths

One theory is that there's a kind of balancing act going on in the human genome. Highly psychopathic individuals make up about 1 percent of the human population. According to this theory, this number is so low because psychopaths are a kind of social parasite that can only thrive in groups predominantly made up of people who can be taken advantage of; that is, environments made up of moral, empathetic, socially-minded individuals. In groups like these, its easier to take advantage of others' trust to gain resources, like access to sexual partners. If there were too many psychopaths, then this system wouldn't work, and a given social group might become stricter about enforcing group norms. It should be noted that this a difficult theory to test directly.

There's also the idea that the "fast" lifestyles of psychopathic individuals may encourage them to reproduce more frequently, but it doesn't encourage them to invest any of themselves in their offspring's success. Individuals with "slow" lifestyles have fewer children but tend to stick around to make sure their children develop into healthy, competent, and successful adults. The psychopath wouldn't care about that — they demand instant gratification and aren't particularly attracted to the promise of future rewards. In this way, fewer offspring with the psychopathic genome would go on to be in a position to reproduce.

Evolution doesn't have a perspective or an opinion on things. It's a neutral process that selects what works. What these studies show is that, at least when it comes to human evolution, psychopathy is more of a feature than a bug.

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Are modern societies trying too hard to be clean, at the detriment to public health? Scientists discovered that a microorganism living in dirt can actually be good for us, potentially helping the body to fight off stress. Harnessing its powers can lead to a "stress vaccine".

Researchers at the University of Colorado Boulder found that the fatty 10(Z)-hexadecenoic acid from the soil-residing bacterium Mycobacterium vaccae aids immune cells in blocking pathways that increase inflammation and the ability to combat stress.

The study's senior author and Integrative Physiology Professor Christopher Lowry described this fat as "one of the main ingredients" in the "special sauce" that causes the beneficial effects of the bacterium.

The finding goes hand in hand with the "hygiene hypothesis," initially proposed in 1989 by the British scientist David Strachan. He maintained that our generally sterile modern world prevents children from being exposed to certain microorganisms, resulting in compromised immune systems and greater incidences of asthma and allergies.

Contemporary research fine-tuned the hypothesis, finding that not interacting with so-called "old friends" or helpful microbes in the soil and the environment, rather than the ones that cause illnesses, is what's detrimental. In particular, our mental health could be at stake.

"The idea is that as humans have moved away from farms and an agricultural or hunter-gatherer existence into cities, we have lost contact with organisms that served to regulate our immune system and suppress inappropriate inflammation," explained Lowry. "That has put us at higher risk for inflammatory disease and stress-related psychiatric disorders."

University of Colorado Boulder

Christopher Lowry

This is not the first study on the subject from Lowry, who published previous work showing the connection between being exposed to healthy bacteria and mental health. He found that being raised with animals and dust in a rural environment helps children develop more stress-proof immune systems. Such kids were also likely to be less at risk for mental illnesses than people living in the city without pets.

Lowry's other work also pointed out that the soil-based bacterium Mycobacterium vaccae acts like an antidepressant when injected into rodents. It alters their behavior and has lasting anti-inflammatory effects on the brain, according to the press release from the University of Colorado Boulder. Prolonged inflammation can lead to such stress-related disorders as PTSD.

The new study from Lowry and his team identified why that worked by pinpointing the specific fatty acid responsible. They showed that when the 10(Z)-hexadecenoic acid gets into cells, it works like a lock, attaching itself to the peroxisome proliferator-activated receptor (PPAR). This allows it to block a number of key pathways responsible for inflammation. Pre-treating the cells with the acid (or lipid) made them withstand inflammation better.

Lowry thinks this understanding can lead to creating a "stress vaccine" that can be given to people in high-stress jobs, like first responders or soldiers. The vaccine can prevent the psychological effects of stress.

What's more, this friendly bacterium is not the only potentially helpful organism we can find in soil.

"This is just one strain of one species of one type of bacterium that is found in the soil but there are millions of other strains in soils," said Lowry. "We are just beginning to see the tip of the iceberg in terms of identifying the mechanisms through which they have evolved to keep us healthy. It should inspire awe in all of us."

Check out the study published in the journal Psychopharmacology.