Biological Theories

Scientists have long been fascinated by whether criminality is written in our biology. These theories suggest that physical characteristics, brain structure, or genetic makeup might predispose someone to criminal behaviour.

The biological approach represents a major shift from earlier moral and religious explanations of crime. Instead of just saying criminals are "evil," researchers started measuring and studying actual physical evidence to understand why people break the law.

Physiological Theories

Physiological theories focus on how our body shape, brain structure, and physical health might influence criminal behaviour. These approaches treat crime like a medical condition that can be diagnosed and potentially treated.

Rather than looking at social factors like poverty or upbringing, physiological theories argue that the answers lie within our physical bodies. This scientific approach has produced some surprising findings about the connection between biology and behaviour.

Theory 1 - Lombroso (1876)

This Italian doctor revolutionised criminology by being the first to study crime scientifically rather than just morally judging criminals. Lombroso believed criminals were physically different from law-abiding citizens and represented a separate subspecies of humanity.

He meticulously measured facial features of convicted criminals, identifying patterns like large jaws, low sloping foreheads, and long arms. Different crimes supposedly correlated with specific features - murderers had curly hair and peaked noses, whilst thieves had flattened noses.

Surprisingly, modern technology seems to support some of his ideas. A recent Chinese university study used AI recognition software on 1,856 people and correctly identified 83% of actual criminals, with only 6% of innocent people misidentified.

Key Insight: Lombroso's work marked the beginning of scientific criminology, moving away from purely religious explanations of criminal behaviour.

Theory 2 - Sheldon's Body Types

Sheldon wrote 'Atlas of Men' in 1954, arguing that personality and criminal behaviour are directly linked to body type. He identified three main body types: endomorphs (round and sociable), ectomorphs (thin and introverted), and mesomorphs (muscular and aggressive).

His research focused particularly on mesomorphs, who he believed were more prone to criminal behaviour due to their aggressive and adventurous nature combined with lack of sensitivity. Using correlation studies, he found mesomorphs were indeed overrepresented among criminals.

Sheldon's study involved rating photos of college students and juvenile delinquents on a 1-7 scale based on how mesomorphic they appeared. The delinquents consistently scored higher as mesomorphs than the college students, supporting his theory.

Remember: Correlation doesn't prove causation - just because muscular people commit more crimes doesn't mean muscles cause crime.

Other Biological Theories

Beyond body types and facial features, researchers have explored how brain damage, disease, and neurological conditions might contribute to criminal behaviour. These theories suggest that crime might sometimes result from medical conditions rather than moral failings.

The focus has particularly centred on the prefrontal cortex - the brain region responsible for self-control and decision-making. When this area is damaged, people may struggle to control their impulses and follow social rules.

Theory 3 - Brain Abnormalities

Brain damage, particularly to the prefrontal cortex, appears strongly linked to criminal behaviour. Raine's 1994 study used PET scans to compare the brains of convicted killers with normal brains, revealing significant damage in the killers' prefrontal cortex.

The famous case of Phineas Gage perfectly illustrates this connection. After a metal rod destroyed most of his prefrontal cortex in a work accident, this previously well-mannered railway worker became aggressive and antisocial, eventually losing his job due to bad behaviour.

Dr James Fallon's research comparing normal and psychopathic brains has found consistent differences in brain structure. These findings suggest that some criminal behaviour might result from neurological problems rather than conscious choice.

Food for Thought: If crime is caused by brain damage, should we treat criminals as patients rather than prisoners?

Theory 4 - Disease and Crime

Medical conditions can dramatically alter behaviour, sometimes leading to criminal acts. The 1920s outbreak of encephalitis lethargica (sleepy sickness) provided clear evidence of this disease-crime connection.

This brain inflammation, typically caused by viruses, led to significant personality changes in survivors. Previously law-abiding citizens developed aggressive tendencies and engaged in abnormal sexual behaviour after recovering from the illness.

Such cases demonstrate how biological factors like disease can directly influence criminal behaviour, supporting the idea that not all crime stems from social or psychological causes.

Key Point: Understanding disease-related crime could help develop medical treatments to prevent certain types of criminal behaviour.

Genetic Theories

Genetic theories explore whether criminal tendencies can be inherited through DNA. These studies examine families, twins, and adopted children to determine how much of criminal behaviour is "nature" versus "nurture."

By comparing people with different genetic relationships, researchers can isolate the influence of genes from environmental factors. This approach has produced some of the most compelling evidence for biological influences on crime.

Theory 5 - Twin Studies

Twin studies provide powerful evidence for genetic influences on crime by comparing identical twins (100% shared genes) with non-identical twins (50% shared genes). If crime is genetic, identical twins should show higher concordance rates.

Christiansen's study of 3,596 Danish twin pairs found a 52% concordance rate for monozygotic twins - meaning if one twin had a criminal record, there was a 52% chance the other did too. Dizygotic twins showed only 22% concordance.

However, the fact that identical twins don't show 100% concordance proves that genes alone don't determine criminal behaviour. Environment and choice still play crucial roles in whether someone becomes a criminal.

Reality Check: Genes might load the gun, but environment and personal choice pull the trigger.

Theory 6 - Adoption Studies

Adoption studies cleverly separate genetic and environmental influences by comparing adopted children with both their biological and adoptive parents. This design helps determine whether criminal behaviour comes from genes or upbringing.

Mednick's study of 14,000 adopted Danish sons found a 20% concordance rate with biological parents versus 24.7% with adoptive parents. Later research showed adoptees with criminal records were more likely to have biological parents with criminal histories.

These findings suggest both genetic and environmental factors contribute to criminal behaviour. The slightly higher concordance with adoptive parents indicates that upbringing and social environment remain incredibly important in shaping behaviour.

Bottom Line: Crime appears to result from a complex interaction between genetic predisposition and environmental influences - it's not simply nature or nurture alone.