For as long as laws have existed, people have been breaking them. After all, crime isn’t inherent to humans - the line between legal and illegal activities is determined by society. What one culture deems unlawful, another allows. Nonetheless, most cultures agree that acts such as murder, assault, and theft constitute major crimes.

However, the biological theory of crime proposes that crime is somewhat predetermined by our internal makeup. We will discuss what this theory entails, and also touch on other relevant terminology. In addition, we will explore its history, and then move on to modern theories of crime.

Biological Theories of Crime: The Definition

Before we define this theory of crime, we should explain what biological positivism is. Positivism is a broader school of thought that biological theories of crime fall under: Biological positivism theory attempts to explain human behavior via physical causes.

Therefore, biological theories of crime combine crime and biology. These theories try to explain what causes someone to commit a crime by analyzing their physical, genetic, and neurological features. According to the features they examine, all biological theories of crime can be divided into three categories:

  1. Approaches that identify criminals according to their physical appearance
  2. Theories that link criminal behavior to genetics
  3. Ideas that try to explain criminal tendencies by looking at distinguishing features in the brain and the body

The oldest theories of this type focused solely on the biological aspect, believing that criminals are born and not made, while some modern offshoots include external factors, as well.

In contrast to biological theories, classical theories presumed that committing a crime is strictly a choice that doesn’t correlate with any external factors or distinct biological characteristics. Both approaches have been proven overly extreme, but it’s rare for an older theory - i.e., classical thought - to be more in line with scientific evidence than a younger one. Nonetheless, that is the case here, as we will see.

A Brief Historical Overview of Biological Theories of Crime

Biological Atavism in Criminology (1876)

Cesare Lombroso, a prison psychiatrist, is often credited with presenting the first biological theory of crime in the 19th century. This is, in fact, a myth, as scientific explorations of lawbreaking had been alive and well before that, but Lombroso’s ideas were in line with the current trend of applying Darwinistic principles to social issues, and therefore gained traction.

Lombroso published a book titled Criminal Man in 1876. The author’s ideas were based on his own analysis of the appearance and psychological characteristics of inmates, in light of the “theory of atavisms.” This idea is believed to have been first introduced by French botanist Antoine-Nicolas Duchesne. The term stems from Latin atavus, meaning ancestor.

Atavisms represent “reverting to ancestral traits;” applied to criminal activity, they are used as an explanation for supposed “regressions” in terms of physical and psychological development, which result in acts that were acceptable in the times of our ancestors, but not in current society.

In his work, Lombroso theorized that anyone who was born a criminal could be identified based on their physical characteristics. For instance, he claimed that all people with criminal tendencies have “enormous jaws, high cheekbones, and prominent superciliary arches.” Of course, just like all other theories relating physical appearance to psychological predispositions, this idea has long since been disproven; any connections stem from the stereotyping of marginalized communities, and not actual biological links between facial features and behavioral patterns.

Although this theory was severely criticized, and rightfully so, it has left a permanent footprint in the history of the biological theory of crime due to its alignment with evolutionary theories of human development and the then-prevalent desire to apply those principles to every aspect of human existence. Its popularity led to a chain of other, similarly misguided, approaches to exploring crime and its causes.

The Theory of Somatotypes (1942)

In 1942, William Sheldon proposed the theory of somatotypes, but it did not apply only to criminals. Similarly to Lombroso, he focused on physical appearance as a distinguishing characteristic between types of people.

Sheldon believed that all body types could be divided into three categories, each corresponding to specific personality characteristics. These somatotypes include the following:

  • Endomorph: This body type is typically overweight, and has wide hips, but slim ankles and wrists. They are laid-back social butterflies.
  • Ectomorph: This somatotype is slim and has a narrow body frame. Ectomorphs are more introverted.
  • Mesomorph: The individuals belonging to this group are muscular, have broad shoulders, and narrow hips. They are courageous and enjoy going on adventures. They can be very assertive, but also aggressive.

The author considered mesomorphs the type that tends to exhibit criminal behavior the most. Just like all its predecessors, this biological theory of crime sparked major criticism. One flaw outlined by other researchers is the fact that Sheldon considered the body type to be genetically determined. However, if that were the case, then there wouldn’t be pairs of monozygotic, that is, identical twins that belong to different somatotypes.

Although most of the scientific community has deemed such theories as having no basis in reality, some researchers have since moved on to formulate newer versions of the same approach. We will discuss them below.

Modern Theories

A modern biological theory of crime focuses on the neurological and genetic components in an attempt to explain the state of mind of a criminal. There are also biological theories that incorporate other fields, as is the case with biosocial views.

Genetics-Focused Theories

Morley & Hall (2003) investigated the effects of genetics and environment on criminal behavior in the wider context of antisocial behavior, including Antisocial Personality Disorder (ASPD), which has been linked to criminal tendencies. They found no links between single or groups of genes and criminal behavior.

The only potentially relevant links have been found between some serotonergic pathway genes and the increased risks of developing disorders sometimes linked to criminal behavior later in life. Further limitations of these studies include only considering the implications of genetics on crimes such as murder or assault, without insight into so-called “white-collar” crimes, as well as consistently overlooking the impact of the environment on the prevalence of criminal behavior, and failing to control for socioeconomic status, which is the most robust predictor for illegal activity.

Grove et al. (1990) conducted a study of monozygotic twins to determine whether there is any correlation between genetics and antisocial behavior, with a focus on alcohol and drug abuse. The significance of this study is that, as opposed to other studies, it included twins that were separated at birth, thus eliminating some of the environmental factors.

The subjects were thirty-one pairs of twins and one set of triplets. Their age ranged from 16 to 68. The study showed that there could be some correlation between genetics and antisocial behaviors, particularly substance abuse. Although the subjects didn’t have the same upbringing, environmental factors still played a role. However, these factors were not taken into account in this study.

Neurology-Focused Theories

Neurological theories of crime are based on studying neurological structures and processes to see if they relate to criminal behavior. Such studies involve tracking neurotransmitter levels (e.g., serotonin and dopamine) in the brain.

Dopamine is responsible for the euphoric feeling we get from pleasurable activities. A higher concentration of dopamine has been linked to aggressive behavior, although primarily in studies assessing the risk of suicide for patients with heightened dopamine. Lower serotonin levels have shown to produce similar effects, again primarily in depressed patients at risk of self-harm. While the importance of preventing self-harm is enormous, these studies have lessened explanatory power for determining the role of dopamine and serotonin in antisocial behavior.

It has been suggested that certain hormone disbalances also have an impact on the potential manifestation of antisocial traits. The two hormones that have been the most hypothesized about are cortisol and testosterone.

Low cortisol levels, which is a stress-regulating hormone, can lead to a different perception of stress, and lowered awareness of potential consequences. On the other hand, it has been suggested that higher testosterone levels make someone more prone to aggressive behavior. Finally, both hormones have been found to produce similar results when their doses in the system were reversed. The rationale for this theory is the idea that, generally, males seem to exhibit more violent behavior than females. However, the impact of socialization on such behavior patterns is rarely controlled for in these studies, despite it having an established impact.

Apart from examining the impact of neurotransmitters and hormones, neurology-focused theories of criminal behavior also analyze specific brain parts to see whether any abnormalities impact one’s actions.

The frontal lobe, in particular, has piqued the interest of scientists in relation to potential crime causation. In the review of a range of studies, Brower & Price (2001) found that injuries to the frontal lobe lead to increased aggression in many cases. It’s worth noting here that the prefrontal cortex “houses” higher cognitive function, including self-control processes and executive function, so increased aggression and decreased impulse control after injury are not unexpected. On the other hand, its development largely depends on a person’s early life and upbringing, and can be severely hindered by environmental factors, such as stress due to low socioeconomic status or abuse.

Biosocial Theories

Some researchers have come to the realization that biological characteristics cannot feasibly be used as the only explanation for human behavior. For that reason, a new set of theories emerged that combine sociological and biological aspects. They are referred to as biosocial theories.

These theories take a look at the abovementioned core elements of the biological theory of crime, but also take into account the social factors, such as living in a disruptive home, being bullied by peers, and so on. That’s why there are laws regarding the responsibility of parents to combat the issue of child abuse and neglect.

Biopsychosocial Theories

As its name suggests, biopsychosocial theories of crime involve three disciplines when studying crime causation:

  • Biology
  • Psychology
  • Sociology

One of the modern biological theory of crime examples observed through the prism of sociological and psychological theories of crime includes a case study of the infamous serial killer Theodore Robert Bundy.

Ted Bundy was born on November 24, 1946, in Burlington, Vermont. He was raised by his grandparents, believing they were his parents, and that his mother was his sister. His grandfather was prone to violent outbursts, while his grandmother suffered from agoraphobia and depression. Therefore, his childhood was far from what would be considered ideal.

As a law student, Bundy had a promising future. To the outside world, he seemed to be a charming, albeit shy individual. However, he went on to commit a string of over 30 murders from late 1973 to 1978. His victims were all women. It’s believed that his surface motive was revenge, after his girlfriend ended their relationship.

Biological influences are hard to establish here. Social and psychological factors seem to have taken the lead: Given that Bundy’s grandfather displayed aggressive tendencies, it’s likely that Bundy’s behavior was modeled after that. The environment Ted grew up in is believed to have significantly impacted him, and the confusion and trauma he experienced undoubtedly affected his perception of the world and his place in it, particularly in relation to women.

In psychiatric terms, several disorders have been thrown around when discussing this serial killer. The most prominent three are narcissistic, borderline, and antisocial personality disorder. While it’s likely he suffered from them, their causes in Bundy remain unknown.

One of the tasks of criminal psychology is to glean the psychological factors participating in criminal behavior, and determine their roots. That’s why more research and studies need to be conducted, so as to reach a better understanding of human behavior, and avoid convictions based on bias.

Final Comments

Evidently, no one theory fully explains why one would commit a crime, primarily because criminal behavior is not a fixed phenomenon: What is illegal and what isn’t changes with the law, not through biological factors. Biological theorists assess the causation from the biological angle, looking for causes in neurology, genetics, and physiology. However, since the impact of social and economic factors remains the strongest predictor of antisocial behavior, these theories would do well to at least adopt a part of that explanation.