Biological Explanations Of Deviant Behavior

Do Biological Factors Make Criminals?

Deviant behavior is any behavior that is contrary to the dominant norms of society. Many different theories exist as to what causes a person to perform deviant behavior, including biological explanations, psychological reasons and sociological factors. Here are three of the major biological explanations for deviant behavior. It should be noted that all of the following theories have been discredited since their inception.


Biological Theories of Deviance 

Biological theories of deviance see crime and deviant behavior as a form of illness caused by pathological factors specific to certain types of individuals. They assume that some people are "born criminals" — they're biologically different from non-criminals. The underlying logic is that these individuals have a mental and physical inferiority which causes an inability to learn and follow rules. This in turn leads to criminal behavior.

Lombroso’s Theory

An Italian criminologist in the mid- to late 1800s, Cesare Lombroso rejected the Classical School that believed crime is a characteristic of human nature. Lombroso instead believed that criminality is inherited and he developed a theory of deviance in which a person’s bodily constitution indicates whether he 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.

Sheldon’s Theory of 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, fragile, lean, lightly muscled, small shouldered and thin. Celebrities that might be described as ectomorphs include Kate Moss, Edward Norton and Lisa Kudrow.

Endomorphs are considered soft and fat. They are described as having underdeveloped muscles and a round physique. They often have difficulty losing weight. John Goodman, Roseanne Barr and Jack Black are all celebrities who could be considered endomorphs.

Mesomorphs are muscular and athletic. Their bodies are described as hourglass-shaped when they're female, or rectangular-shaped in males.

They're muscular, they have excellent posture, they gain muscle easily and they have thick skin. Famous mesomorphs include Bruce Willis and Sylvester Stallone.

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

The Y Chromosome Theory

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 within 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 higher than the general male population — 1 to 3 percent to less than 1 percent. Other studies don’t provide evidence that supports this theory, however.


BarCharts, Inc. (2000). Sociology: The Basic Principles of Sociology for Introductory Courses. Boca Raton, FL: Bar Charts, Inc.

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Crossman, Ashley. "Biological Explanations Of Deviant Behavior." ThoughtCo, Jan. 8, 2017, Crossman, Ashley. (2017, January 8). Biological Explanations Of Deviant Behavior. Retrieved from Crossman, Ashley. "Biological Explanations Of Deviant Behavior." ThoughtCo. (accessed March 22, 2018).