Home
Genetic Theories
- Explanations of criminal behavior that rely on genetics as the main cause generally fall into one of three main groups: YYX chromozone theory, twin studies and adoption studies.
- The YYX Chromozone Theory suggest that there is an unusual genetic strucure in some men that produces very aggressive behavior. This aggressive behavior is the result two Y sex chromozones rather than the normal one. This condition is considered to be very rare and could not explain most violent behavior however. It is also believed that because the condition is so rare, valid research would be very difficult to achieve. It could be very difficult to know the number of men with doulble Y chromozones that have ever committed a crime.
- Twin studies are used to show the affects of genetics in behavior. This is possible because identical twins have the same genetic make up and can be compared with non twins for the frequency of criminal behavior. If twins commit criminal behavior at a greater frequency than non twin siblings this would suggest a role for genetics in criminal behavior.
- With adoption studies the goal differentiate the role that enviroment plays from that of genetics.If children who are raised by non-relative adoptive parents show a geater similarity to the behavior of thier biological parents, who had no enviromental influence, then it would suggest genetic influence.
- In one famous adoption study the following results were reported
- Of the children studied who had no criminal behavior in either thier adoptive or biological parents in was found that 13.5% committed delinquent acts.
- Of the children studied who had criminal behavior in thier adoptive parents but none in thier biological parents in was found that 14.7% committed delinquent acts.
- Of the children studied who had no criminal acts in thier adoptive parents but did in thier biological it was found that 20% committed delinquent acts.
- In children that had criminal acts in both set of parents it was found that 25% committed delinquent acts.
- This was seen as giving strong evidence to the theory that genetics plays a role in cuasing criminal behavior.One of the important findings however was that in all groups the vast majority of children committed no deliquent behaviors.
- In a famous twin study conducted between 1929 and 1961 found the following results:
- 60% of identical twins had the same criminal behavior pattern while only 30% of nonidentical twins had a similar pattern. This also lends evidence that genetics plays a role in determeining criminal behavior.
- Similar corelations have been found in other twin studies