Biology 202, Spring 2005
Third Web Papers
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Is Michael right, are we all monsters? Does everyone has these feelings? What stops us from going on killing sprees, and when other people do why we enjoy hearing about it? Humans are the only known species that feels the need to kill within its species for fun. Other animals work on an inhibition mechanism to not kill one of its own species without reason. Something must have happened in our evolutionarily history that would explain why we developed differently. Some say it is the development of complex emotions, and civilization that make up for the lack of inhibitory mechanisms to not kill within our species. However humans still injury and hurt each other for no apparent reason, so our normal ways of inhibiting ourselves from hurting each other are not working ((2)). Some say these violent crimes against each other can be attributed to an inability to use logic and rational to access a situation before making a decision. Until recently, people believed it was mostly environment that determined whether or not violent behavior was expected. However new research is saying otherwise, genetics and nutrition could play up to a 50% role in violent behavior ((3)).
The desire to "pin down" the nature of evil, violence, or aggression in human beings has had a long history, as far back as the 17th century. The concept of human nature has been through many phases starting with the belief that humans were neutral creatures- neither inherently good nor inherently bad. We are shaped entirely by our circumstances and environment. Through time the belief has fluxed between thinking humans are inherently good or we are inherently bad. Charles Darwin was the first to see humans as having not only shared/similar characteristics with animals, but that human beings are bound to the same laws of competition, survival and natural selection, as animals are. The idea that human behavior could in any way be dependant on instinct was a radial conclusion, and Darwin's theories still stir debate today. However, the infamous Sigmund Freud, father of psychoanalysis, was the first to really define instinct as a drive inside of you that you cannot control. Animal behavior is completely controlled by instinct, and human behavior is at least partly controlled by instinct. Freud' theory says that the basics drives for humans are to reproduce and also to destroy ((2)).
Is Freud just a sick man, with a pessimistic view of the human mind and its capabilities? Freud's theories have been highly accepted, though controversial, and if nothing else serve as a good starting place for exploring the "nature verse nurture" debate. If Freud is correct, then there must be something inside of us that controls our emotions, particularly aggression. Combining the theories of Darwin and Freud would mean that there is some reason which humans have adapted to being aggressive. Being aggressive to other animals takes energy, and natural selection would not select for a trait that wastes energy. In other words, aggressive behavior has been selected for rather than non-aggressive traits. If aggressive behavior can and had been selected for, then there must be something genetically controlling it. There must be something more than environment affecting violent and destructive behavior in humans.
Waller, in his book Becoming Evil, gives an explanation as to why humans have the potential to be so destructive. He says that we are less than 10,000 generations away from being hunter-gatherers. Our ancestors needed to be aggressive in order to eat and survive; however the evolution of traits has not had enough time to catch up with our development. Modern day lifestyles do not require us to hunt for our food, or fight for our survival. Waller comments, "there is often be a lag in time- very substantial in the case of human evolution- between a new adaptive problem and the evolution of the mechanism designed to solve it" ((2)) . The human brain is still highly evolved to living in a hunger-gatherer type of lifestyle, even though new developments have allowed us to surpass our ancestors.
Combining modern day technologies such as guns, bombs and other advanced weaponry with the hunter-gather mindset can be a deadly mix. With violent crime rates on the rise, the search for the genetic answer to aggression has never been more needed. The latest research has shown that a smaller prefrontal cortex in the brain can lead to aggressive and very violent behavior. The prefrontal cortex is found right behind the eyes and is believed to play a critical role in self- restraint and rationalization of emotions. It is also a key component in feeling guilt, remorse and experiencing social awareness. Using brain-mapping technology, scientists were able to find that even a reduction of 11% of the prefrontal cortex nerve tissue leads to antisocial and violent behavior ((4)).
One factor believed to at least help with aggressive behavior in small children is proper nutrition. Good nutritional habits help promote brain growth and function in developing humans, so by eating better, even during pregnancy can potentially help with aggressive behavior. Also a diet rich in omega -3 fish oil showed a reduction in antisocial behavior even in adults ((3)). The concept that food, or nutritious elements found in our food can have an impact on our brain and therefore behavior is more evidence that aggressive behavior does have a large biological component to it.
An equally interesting study dealt with the idea of revenge. "Tagged" water was followed through out the body and the brains of men playing a card game. The men, when another player cheated, could decide if they wanted to get revenge on the other person by taking away some of their points. However, when the stakes were too high, or too risky the players who could get revenge usually decided against it. So even though the player wanted revenge, they decided against it. The results found were that the area of brain activated the most for revenge was the dorsal striatum, however it is interesting to note that the prefrontal cortex was also highly active when the player was weighing the risks between punishing/ getting revenge on another player or deciding that the risks were to high. A researcher comments, "In fact, I believe that our evidence shows that people deal quite rationally with their emotions"( (5)). This implies that indeed the prefrontal cortex does seem to control what emotions we choice to act on or not act upon, and without a fully functional prefrontal cortex people are less likely or maybe incapable of rational decision making.
Other researchers are studying specifically chromosomes and looking for any inherent differences in our genetic makeup itself that would lead to abnormal, violent behavior. Males born with the chromosome combination of XYY are believed to be more inclined to commit dangerous and violent crimes. Known to be very tall, have a small IQ, and low fertility XYY men could be genetically predisposed from birth to be aggressive. Tests done in mental hospitals in the United Kingdom found that 7 men, all who had committed violent crimes, had XYY chromosomes ((6)). One flaw in jumping to the conclusion that because a man is XYY he is therefore a threat to society is that only men who had been already convicted of crimes had been tested. There could be plenty of XYY men living perfectly normal lives without any record of abnormal behavior because they have none anything wrong, but they do not factor in the study results because only men previously convicted were tested. Therefore it is hard to say that all XXY men are predisposed to abnormal behavior.
If all humans, seeing as we all came from the same ancestors, have the potential to be destructive why aren't we? Culture and the rise of civilization has something to do with it. We learn to control our impulses or instincts as young children. We learn quickly that we will be punished if we do something wrong. If we do not fear punishment from other people, we fear punishment from ourselves in the form of guilt. People who are lacking this ability to learn "right from wrong" and rationalize their actions are the ones who actually lash out and do violent things. Whether or not the size of the prefrontal cortex or an extra Y chromosome are the genetic causes to aggression is still unclear.
It would be interesting to see more research on the nutrition end of the discussion and how it could affect the size of the prefrontal cortex. Also an analysis of the evolution of XYY to see if it was more prevalent 10,000 years ago or if the numbers of XYY men are on the rise. Maybe there are so few known XYY males because national selection is beginning to select against this genetic combinations because aggressive behavior is no longer needed in our society. One other major flaw in all current research is the lack of study of violent woman. There have been no recorded links between genetics and female aggressiveness.
If all the newest research is correct then we could one day be able to determine based on genetics or brain size, whether or not someone will be violent. Does this mean we have to the right to punish them, is it their fault that they lack the metal abilities to adjust to our society rather than the ones of our hunter- gatherer ancestors? I would say no, because any genetic explanation for aggression or violence can not completely explain our behavior. Even serial killers turn themselves in because they know they are doing something wrong, or something is not right with their actions even if they can not stop themselves. Clearly environment and circumstances affect human behavior. The debate is only to figure out what the ratio is between the factors and how genetic factors can be minimized.

Works cited
1) Quotation website
2) Waller, James. Becoming Evil. New York: Oxford University Press, 2002.
3) Raine, Adrian. Biological Key to Unlocking Crime
4) Size of Brain Linked to Violence
5) Roach, John. Brain study Shows Why Revenge is So Sweet
6) Blame It On Your Genes
Works consulted
1. Levin, Jack. Mass Murder America's Growing Menace. New York: Plenum Press, 1985.
2. Stream DR. Herbert. Our wish to Kill. New York: St. Martin's Press, 1991.
3. Tithecott, Richard. Of Men and Monsters. Madison: The University of Wisconsin Press, 1997.


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