The truth is we're all sinners – it's how we survive as human beings

On 21 April 1992, Robert Alton Harris was led to the gas chamber in San Quentin prison, his final meal a 21-piece bucket of KFC, two Domino’s pizzas, and a bag of jellybeans, washed down with a six-pack of Pepsi and a pack of Camel cigarettes. His fellow prisoners considered him such a terrible human being they celebrated his execution.

His journey to his early death had started many years before, in 1978. He and his brother had kidnapped two teenage boys at gunpoint, stealing their car for later use in a bank robbery. According to his brother, Harris had shot the boys in the back. One ran away, and he chased the boy down, held the gun to his temple and blew his head off. In the aftermath of the double murder, Harris was described as elated, polishing off the burgers the boys had bought just before the kidnapping. He joked to his brother that they should impersonate police officers, and report the boys’ deaths to their parents.

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Harris was clearly a monster, a man devoid of empathy or kindness. But his story is one that illustrates the complexities of nature versus nurture, of free will, of what it means to be human. For from another perspective, his journey to the gas chamber had started decades earlier, before he was born.

His parents were both alcoholics, and he had been born premature after his father kicked his mother in the stomach, convinced that Harris was the product of infidelity. He had a speech impediment and learning difficulties, attributed to his mother’s drinking in pregnancy. His father beat all his children mercilessly, and sexually abused his daughters, and his mother denied Harris any physical contact. Aged 14, he was in detention for trying to steal cars, and was raped repeatedly.

To learn of his upbringing does not excuse him of his crimes, but perhaps provides some degree of explanation. Was he the architect of his own life, or was it determined by external factors – a combination of his genes, the stunting effects of alcohol on his brain, the traumatic nature of his childhood?

The Seven Deadly Sins – wrath, gluttony, lust, envy, sloth, greed and pride – have long been held to be the origins of human wrongdoing. These are the markers of immorality, of depravity of the soul. Yet as anyone who works in the area of brain health will attest, it is not unusual to see people with brain diseases or conditions that generate these “sins”.

Individuals who have brain tumours with excessive sexual desires. Seizures causing aggression. Medications causing profound pride. Genetic conditions producing insatiable hunger. What these patients illustrate is that these “sins” originate from the brain, not from the soul.

As our knowledge of the brain expands, we are beginning to learn that myriad factors mould our brains, predisposing us to act in a particular way. Even for those of us without serious neurological diseases, how our brains develop and grow is influenced by a range of elements that are beyond our control.

How we are brought up, the influence of our parents and their parenting style, even how our mothers eat or how much stress they are exposed to when we are still in the womb, leave an imprint on our brains that resides for the rest of our lives. The hormones we are exposed to during pregnancy may drive our personality, even our sexual preference or orientation.

The genes that are present within us from the moment of conception affect our levels of aggression and our appetites. Viruses that we are exposed to or the bacteria within our guts may ultimately control our weight. 

Some neuroscientists, and philosophers too, argue that we have no free will at all, that we are entirely defined by the machinery of our brains, that lump of fatty tissue within our skulls. That for Robert Alton Harris, it was inevitable he would make the “choices” he made. 

The truth is that these “sins” reside in all of us. They are woven into the tapestry of what it is to be human. And there is a clear reason for that. Every one of these “sins” serves a useful purpose, a tool for survival, and is propelled by evolutionary imperatives. Without lust, we are destined to become extinct. Without gluttony, we will starve in times of famine.

Without jealousy, we risk raising children that are not our own. Greed drives us to gain resources that fuel survival; even the thought of money promotes self sufficiency in psychological studies. Sloth reflects the constant calculation of “Is it worth it?” – will the energy I burn be worth the reward at the end of any particular task? Pride and anger drive success, the defence of our resources in the face of threat, and the persistence to achieve.

In that respect we are all born with original “sin”. But for some, these normal human traits are amplified or intensified by nature or nurture, where the physiological becomes pathological. 

Guy Leschziner is a consultant neurologist and professor of neurology and sleep medicine.

Seven Deadly Sins: The Biology of Being Human by Guy Leschziner is out 21 November (William Collins, £22). You can buy it from the Big Issue shop on bookshop.org, which helps to support Big Issue and independent bookshops.

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