In my last blog post, 8 Inverted Isn’t 8, I looked at a gene abnormality in my family. In my family’s case the change of the chromosome could cause multiple defects t
hroughout the body. It got me thinking about how our genes “make us who we are.” On top of that I watch too many crime shows (if you’re wondering, I like Criminal Minds). If you combine those two you have the following question: is killing genetic?
How can you tell a murderer from a normal person?
Many people have tried to deduce what traits killers share to try and get it down to a science.
A very famous Italian, Cesare Lombroso, also know as the father of modern criminology tried to deduce what makes a killer. Most of his theories shine in his works Criminal Man and Criminal Woman, the Prostitute and Normal Women. He believed that criminals were born to be just that. He would sit down and study hundreds of faces and characteristics of criminals to find connections. This is the guy who thought that criminals had big ears and hairy arms. Source. He is also the man who said killers were left handed and used the word ‘idiot.’ Source. Unfortunately most of his work has been discredited; however, he started the conversation about predispositions for killing.
What about your genes or biological factors?
In 1968 there was a spike of research about extra sex chromosomes. It was shown that 3% men in prison has an extra Y chromosome. Many people then believed that men who were XYY were more likely to kill. This was discredited due to the small percent of men it effected in prison. Source.
A new type of gene based criminology is springing up called neurocriminology. Adrian Raine, a professor at University of Pennsylvania, is leading the way with his work with criminals. He took brain scans of 42 of murders and compared them. He noticed a great number of criminals has a reduced prefrontal cortex. This is caused by abuse, lead exposure, alcoholic pregnancy, head trauma when the person is young that caused damage to it. Raine believes that killers are created through ½ genetics and ½ environmental factors. Source.
However, not all killers he studied had reduced prefrontal cortex activity. Some had a small amygdala, the part of the brain that is our remorse and conscience. Men with a reduced amygdala are 33.3% more likely to perform acts of violence. Source.
A study conducted by scientist at the University of Wisconsin-Madison, agreed with Raine’s results; except, this study linked psychopathy to a reduced amygdala. Source.
“Isn’t psychopathy a mental illness?”
Psychopathy is defined as “a mental disorder in which an individual manifests amoral and antisocial behavior, lack of ability to love or establish meaningful personal relationships, extreme egocentricity, failure to learn from experience, etc.” Source. Famous serial killer Ted Bundy suffered from psychopathy. Source. Yes it is a mental illness, but if you a smart person you can rationalize that a person who can’t feel remorse will have a smaller amygdala (part that feels remorse) which can be genetic.
The last bit of study to be shown involves the MAOA enzyme. One study conducted in 1993 Netherlands by Han Brunner, followed several men in a single family known for antisocial and aggressive behavior. Source.
It turns out the family was lacking what is called the “warrior gene” which is the gene that tells the body how much MAOA (regulator of neurotransmitted impulses) to make. Basically, with this gene men are more prone to violence if it is activated. As it turns out 30% of men have the warrior gene. Source.
Professor Jim Fallon (his TedTalk on this subject is linked to his name) elaborated on the studies findings “If you’ve the high-risk form of the gene and you were abused early on in life, your chances of a life of crime are much higher. If you have the high-risk gene but you weren’t abused, then there really wasn’t much risk. So just a gene by itself, the variant doesn’t really dramatically affect behaviour, but under certain environmental conditions there is a big difference.” Source.
So is this genetic?
I want to say yes but it isn’t 100% genetic. A lot of external factors, such as environment, play a huge role in your predisposition to violence.
One thing I’m curious about is whether or not there is a difference in the murderers with low activity in their prefrontal cortex versus killers with a small amygdala?
We won’t really know until more studies are done.
This is a topic that I was always so intrigued by. I’ve done reports on the Zodiac killer along with watching shows like Dexter and reading books like American Pyscho. I just never could understand how certain people can truly be so much different than the rest of society. The data here does show some good evidence of explaining that. This blog was done very nicely covering multiple reasons with a lot of sources to back it up. I do feel like genetics have a big part to do with due to the early signs that they show. They show signs such as showing no feelings, setting fires and killing animals. They do such things at ages before they even have the opportunity to let experiences to shape them. I don’t believe all killers were born to kill but many definitely were.
I just would like add that there was no evidence that men with extra Y chromosome actually commit more crime than others.
i found your post really interesting because I just took CRIM 012 in the summer and we covered this topic. I was particularly interested in Lombroso theories because I thought his ideas make no sense. I believe that it is impossible to tell who would be a killer from ones look. I think maybe certain genes do contribute to the development of criminal behavior but environment is the main contributor. I learned many social theories in class such as strain theory (http://study.com/academy/lesson/mertons-strain-theory-definition-examples-quiz.html) , social learning theory (http://criminology.wikia.com/wiki/Social_Learning_Theory), social disorganization theory (http://criminology.wikia.com/wiki/Social_Disorganization_Theory) and so on. Maybe a study can be done which researchers can analyze a group people with reduced pefrontal cortex and another group with normal prefrontal cortex and see the difference between their criminal records or other factor.
This blog was very well done. I found the study on the XYY chromosomes to be particularly interesting. You stated that only 3% of criminals had it, but I wonder if those 3% had anything in common. What I mean is, were a strong number of this 3% a certain type of criminal, such as a murderer or a thief? Maybe the XYY chromosome sticks out more in a certain type of criminal than in others.
I definitely thought that the inclination to kill was innate but I never though of it being in a gene. I found the XYY theory extremely interesting. I agree that a persons’s environment can also cause people to be more likely to react in an irrational way. Just like if a child is neglected and ignored when they are younger, they’re going to ignore they’re child when they’re older (not in all causes, but some). If they are not taught to deal with problems in a rational way when they’re younger, they’re never learn. This actually makes me think of the documentary Blackfish. In the documentary, the main male whale, Tilikum, is mated with the females and since he has the inclination to kill, his offspring are more aggressive and violent.
I really never thought about genes having an influence on killers. I found your research very interesting,especially where you talk about how the killers have a reduced prefrontal cortex. As you said there are many reasons why this happens such as alcoholic pregnancy,head trauma ect. I think this shows that these things are what influenced them to become killers. For example, alcoholic pregnancy didn’t make them killers but it shows that they had a very hard time during their life. Also had trauma could mean as a kid they were beaten or hurt which resulted them to become the killers they are. This could mean thats it maybe more of the persons environment that they grow up in rather than just genes causes them to become murderers.
You’re post immediately caught my attention, I am really interested in psychology and how serial killer get to be who they are. Although there are genes that can promote violence, I think that serial killers though processes are killing stem from their childhood. Almost every serial killer has a history of some type of child abuse, and I believe that’s what makes them who they are. In the “Incidence of Child Abuse in Serial Killers” by Heather Mitchell and Michael Aamodt of Redford University they found shocking statistics. “For the 50 serial killers, the following breakdown of abuse was found:
Some type of maltreatment, re- gardless of abuse type (68%)
Physical abuse (36%)
Sexual abuse (26%)
Psychological abuse (50%) Neglect (18%)
No abuse (32%)”.
Their research shows that there is a large amount of maltreatment involved in the life of a serial killer as a child. In my opinion, nobody is born a killer, their envuronment turns them into one.
Here is a link to the journal: Journal
I find it fascinating that there are possible connections between the anatomy of the brain and the level of violence of an individuals. However, I must agree that the environment one grows up in plays a huge role, if not the greatest, in how violent someone is. A study (found here: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC539471/) found that, “individuals saw aggression as a legitimate way to deal with challenges,” and perhaps that is why those abused as children or who grew up in a rough environment turn to violence to help their release anger.