Why Some Biological Explanations for Deviancy Have Been Discredited

Museo di Antropologia Criminale “Cesare Lombroso”
régine debatty/Flickr/CC BY-SA 2.0

A number of theories have tried to explain why people take part in deviant behavior, which is defined as any behavior that goes against the dominant norms of society. Biological explanations, psychological reasons, and sociological factors have all been linked to such behavior, but three of the major biological explanations for deviancy have been discredited. They posit that criminals are born rather than made, meaning that one's genetic makeup is the top reason a person engages in deviant acts.

Biological Theories 

Biological theories of deviance see crime and deviant behavior as a form of illness caused by distinct pathological factors. They assume that some people are "born criminals" or that offenders are biologically different from the general public. The logic here is that these individuals have a mental and physical defect of some sort that makes it impossible for them to learn and follow rules. This "defect," in turn, leads to criminal behavior.​

Born Criminals

Nineteenth-century Italian criminologist Cesare Lombroso rejected the idea that crime is a characteristic of human nature. Instead, he believed that criminality is inherited, and he even developed a theory of deviance that argued a person’s bodily constitution indicates whether one is a born criminal. These born criminals are a throwback to an earlier stage of human evolution with the physical makeup, mental capabilities, and instincts of primitive man.

In developing his theory, Lombroso observed the physical characteristics of Italian prisoners and compared them to those of Italian soldiers. He concluded that the criminals were physically different. The physical characteristics he used to identify prisoners included an asymmetry of the face or head, large monkey-like ears, large lips, a twisted nose, excessive cheekbones, long arms, and excessive wrinkles on the skin.

Lombroso declared that males with five or more of these characteristics could be marked as born criminals. Females, on the other hand, only needed as few as three of these characteristics to be born criminals. Lombroso also believed that tattoos are the markings of born criminals because they stand as evidence of both immortality and insensitivity to physical pain.

Body Types

William Sheldon was an American psychologist practicing in the early to mid-1900s. He spent his life observing the varieties of human bodies and came up with three types: ectomorphs, endomorphs, and mesomorphs.

Ectomorphs are thin and fragile. Their bodies are described as flat-chested, lean, lightly muscled, and small shouldered.

Endomorphs are considered soft and fat. They are described as having underdeveloped muscles and a round physique. They often have difficulty losing weight.

Mesomorphs are muscular and athletic. Their bodies are described as hourglass-shaped when they're female, or rectangular-shaped in males. They're muscular with thick skin and have excellent posture.

According to Sheldon, mesomorphs are the most prone to commit crime or other deviant behaviors.

Y Chromosomes

This theory holds that criminals have an extra Y chromosome that gives them an XYY chromosomal makeup rather than an XY makeup. This creates a strong compulsion in them to commit crimes. This person is sometimes called a "super male." Some studies have found that the proportion of XYY males in the prison population is slightly higher than the general male population, but other studies don’t provide evidence that supports this theory.


  • Gibson, Mary. "Born to Crime: Cesare Lombroso and the Origins of Biological Criminology (Italian and Italian American Studies)." Praeger, 2002.
  • Rose, Martha, and Wayne Mayhall. "Sociology: The Basic Principles of Sociology for Introductory Courses." BarCharts, Inc., 2000.
mla apa chicago
Your Citation
Crossman, Ashley. "Why Some Biological Explanations for Deviancy Have Been Discredited." ThoughtCo, Aug. 27, 2020, thoughtco.com/biological-explanations-of-deviant-behavior-3026265. Crossman, Ashley. (2020, August 27). Why Some Biological Explanations for Deviancy Have Been Discredited. Retrieved from https://www.thoughtco.com/biological-explanations-of-deviant-behavior-3026265 Crossman, Ashley. "Why Some Biological Explanations for Deviancy Have Been Discredited." ThoughtCo. https://www.thoughtco.com/biological-explanations-of-deviant-behavior-3026265 (accessed April 10, 2021).