An intriguing evolutionary hypothesis examines why people harm themselves – and how they have moved to safety for millennia.
ILLUSTRATION: N. CARY / SCIENCE
When a respected evolutionary psychologist named Nicholas Humphrey co-organized a symposium several years ago, he sought an expert to teach a mystery from the time of Charles Darwin explore. "Natural selection will never produce something in a being that harms oneself," wrote Darwin in On the Origin of Species.
But in humans, natural selection apparently did just that. Suicide is the leading cause of death. Every year, about 800,000 people die worldwide ̵
Humphrey, emeritus professor at the London School of Economics, knew this. A handful of evolutionary thinkers had offered ways to solve this paradox. But he found no explanation for most cases of suicide. Therefore, he decided to investigate the topic and to give the lecture itself.
Humphrey turned an evolutionary eye to epidemiological data and human cultures and concluded that suicide was probably the tragic byproduct of a vital adaptation: the sophisticated human brain. When he published an article about his work after the conference, he found that another researcher had similar ideas. A psychotherapist named Clifford Soper, who is now in private practice in Lisbon, had his doctorate. Work that concludes that the devastation of suicide is a consequence of human intelligence and has shaped our minds and cultures. And some clinicians may fear that vulnerable people might misinterpret the idea that suicide is "natural." In fact, Humphrey and Soper suggest that what makes us human endangers us and saves us. They argue that people have developed a range of defense mechanisms, such as religious beliefs, that are critical to our culture and psychology, given the ongoing risk of suicide.
"People very rarely die from suicide because we are well-engineered to deal with whatever life throws at us, but our suicidal response is not fail-safe," says Soper. He suggests that these hypotheses could help explain why suicide is often impulsive, and also draw attention to effective prevention strategies.
Ideas shatter the field, says evolutionary psychologist Todd Shackelford of Oakland University in Rochester, Michigan. By shifting the focus to natural suicidal defenses, Soper has "turned everything upside down," says Shackelford, an outside reader of Sopers thesis. "He can be completely wrong. But he is pushing the field in new directions.
SOPER WAS PART-TIME IN 2014 Psychotherapist. He lived in Gloucestershire in the UK and wanted to understand the origins of suicide in order to help people who mourn him. As he scoured the scientific literature, he was fascinated by the power of evolutionary thinking that seemed "more useful than anything else," he says.
Soper finally earned his doctorate. 2017 at the School of Natural and Social Sciences, University of Gloucestershire, Cheltenham. "What I thought was so strange that I knew I needed peer review," he says. "I needed people who talk back."
Soper calls his model pain and brain: When a sophisticated mind is confronted with excruciating pain, he can regard death as an escape. In developing the model, he started from familiar facts. All organisms feel pain that is essential to avoiding threats. But humans are probably unique in our big brain, which allows us a complex social life, a complex culture and an awareness of death.
Humphrey followed similar considerations. He and Soper say the combination could explain why suicide is unique and widespread in humans, as it has been reported in all types of human society, as diverse as hunter-gatherer groups and industrialized nations. A 4000-year-old Egyptian poem mentions suicide, as well as historical records from all periods since. Humphrey also notes that suicidal and suicidal behaviors are far more common than the act itself. In the United States, according to the National Drug Use and Health Survey, about 4% of adults or nearly 10 million people consider suicide serious in 2017. This is more than 200 times the number of suicide victims this year.
In contrast, Humphrey and Soper find no convincing evidence that other animals intentionally end their lives. And although suicide rates among US youth are rising, child suicide remains extremely rare: Of the more than 47,000 people in the US who died of suicide in 2017, only 17 were between 8 and 10 years old; In recent years, such deaths were not reported.
Although suicide occurs in all human cultures, it is also a rare event. Soper and Humphrey point out that many cultures try to fight suicide by stigmatizing or making it unthinkable. All great religions forbid at least some forms of suicide, so Soper, as well as many tribal customs. For example, Soper notes that Baganda in Uganda is destroying the homes of people who die by suicide and banish their relatives, as other scientists have documented.
Such defenses are perhaps the easiest to recognize when they collapse. Doctors and others have long feared a suicide infection – for example, after the widespread death of a celebrity. According to a study in PLOS ONE (19459017), the death of actor Robin Williams last year was connected with 1800 more suicides in the following months. Research cited by both Soper and Humphrey reported shocking annual 1.7% suicide rates in certain villages on the island of Palawan in the Philippines. There, anthropologists reported that suicide was casually discussed and villagers believed little in life after death. In a 2014 long-term study, the researchers found that US adolescents who committed suicide among friends and relatives often experience suicidal thoughts and sometimes suicide attempts. "Against suicide there are cultural protections that weaken," says sociologist Anna Mueller of Indiana University in Bloomington, who co-authored this study in the American Sociological Review (19459016).
The role of religion can be complex, warns sociologist Bernice Pescosolido, also from Indiana University. Her studies in the United States suggest that, regardless of her doctrine, a religion is likely to protect herself from suicide if she maintains close-knit social networks.
Most controversial is Soper's view that mental illness can itself be a protection against suicide. He suggests that certain mental disorders are associated with suicide, as they were developed by natural selection as the last line of defense against suicide. For example, he argues that the lack of an initiative that accompanies depression can help prevent suicide bombers.
This argument is plausible for some types of depression, says Riadh Abed, chair of the evolutionary psychiatry group at the Royal College of Psychiatrists in London. But he and several other psychiatrists are skeptical of Soper's arguments about other illnesses – for example, compulsive drug use and addiction can sometimes relieve unbearable pain and reduce suicides.
Even Shackelford says such ideas require further testing and other scientists find them on the edge. One critic is the psychologist and leading suicidologist Thomas Joiner of the Florida State University in Tallahassee. Joiner's interest deepened during his schooldays when his father died by suicide, and he investigated the development of suicide because, like Soper, he thought the resulting understanding might help the patient. However, Joiner vehemently disagrees that suicide is a result of a natural human condition.
He suggests that suicide could constitute a misfire of altruistic and self-sacrificing behavior, similar to honeybees that voluntarily sting and invade intruders to protect the nest. Some suicides may falsely believe that they are relieving their relatives. For Joiner, "it could not be clearer" that these deaths are caused by psychiatric illnesses and that suicidal impulses need to be treated as such.
Randolph Nesse of Arizona State University, Tempe, says that he is "fascinated, but not fascinated," meaning "confident," according to Sopers, that man tends to avoid suicide. Nesse stresses that suicide is "a behavior that can have many possible causes and motives," so that it can not adequately explain a unified evolutionary theory.
Despite this criticism, Humphrey hopes that this work can help patients. "I like to think that it could help a person if they could see why they have developed into a brain that is prone to choosing this catastrophic, short-term solution," he says. "A person who sees through the logic behind their suicidal impulses may be the best able to resist them."
For help, call 1-800-273-8255 for the National Suicide Prevention Lifeline or visit https://www.speakingofsuicide.com/resources.