Nature or Nurture? The Determination of Human Behaviour

The nature versus nurture debate has spanned over decades, and is becoming more heated in the recent years. Following the mapping of the human genome, scientists are pursuing the possibility of controlling human behaviour such as homicidal tendencies or insanity through the manipulation of genes. Is this possible for us to ensure that humans behave in certain ways under certain circumstances in future? This is highly doubtful, as the determination of human behaviour depends not only on genes (nature), but also on the environment (nurture).

It is usually the joint product of genes and nvironment, one of the first principles in Leda Cosmides and John Tooby in Evolutionary Psychology: Nature and Nurture (attached). This remains our groups thesis. Take for example this Calvin and Hobbes strip. We assume that duplication is the same as cloning and therefore the two Calvins are genetically similar. Hobbes (that is the tiger) implies in the last frame that the two are similar in behaviour. Ignoring the absurdity, it brings us to a question: Do genetically similar people behave the same way? That is, can nature alone determine how one behaves?

This seems quite impossible. Take another fictitious, but thought-provoking, example in Mowgli, from The Jungle Book by Rudyard Kipling. He is genetically similar to all human beings and much less so to wolves, bears and panthers, but he behave more like the wild animals. In this case, it is certainly clear that nature alone cannot determine human nature. The environment makes a difference. Behaviour genetics Behaviour genetics is the study of the extent to which heredity (genes) influence human behaviour. Genes are found in chromosomes which are made up of deoxyribonucleic acid DNA).

Our DNA strand determines not only our physical characteristics (known to soem as our genetic architecture) but also our psychological make up. The human genome project has isolated certain genes responsible for certain behaviour traits. For example dopamine is responsible for risk-seeking behaviour, as well as hyperactivity (The Economist June 1st). Although the probability of altering genetic make-up and therefore human behaviour is becoming closer to reality, scientists believe that there should not be a dichotomy between nature and nurture (The Economist).

Behaviour genetics include twin studies, family studies and adoption studies. Adoption studies focused on how people with different genetic make-up, brought up in a similar environment may or may not share similar behavioural patterns and family studies on people with the same genetic make-up. The results are not conclusive, although it is found that the possibility of people who are genetically similar, sharing similar behavioural traits is higher. Twin studies remain our interest.

Identical twins have 100% identical genes and the same shared-environment (same home, same parents, same siblings, etc) , and thus any differences etween them will be the non-shared environment (individual friends, own perceptions). Fraternal twins share about 50% of their genes and the same shared-environment. Studies made by comparing behavioural traits in these twins are once again not conclusive: about 40% of the variance in these traits are genetic, 35% non-shared environment and 5% shared environment.

The Nature/Nurture Controversy, Frank Fujita. Attached) The chances of similar genes creating similar behaviour is never 100 percent. The one thing that can be concluded, therefore, is that it takes a combination of nature and nurture to reate behavioural patterns as adherent to our thesis. To make it more evident that nature alone cannot determine human behaviour, we look into group behaviour. Group Behaviour: a biological mystery We learn in history, that in Nazi Germany, the Germans were almost totally indoctrinated.

They were often euphoric at Hitlers speeches, they were incensed to go into war and children in military schools would go as far as to betray their own parents to the secret police. The same occured in Japan, when individuals were blinded by the need of honour and glory for the Emperor. From Jung Changs Wild Swans, which is about China under Mao Zedong, she talks about how people would actually faint with the joy of seeing the great Chariman and about the mad processions in the Cultural Revolution. These behaviour are shared by people who cannot possibly share the same genetic make-up.

We choose to focus on this issue of irrational human behaviour using The Crucible by Arthur Miller. To put it simply and in focus, there is a group of girls who would go into trances and hysterics, faint, scream, et cetera. and accused innocent people of witchcraft. (Most significantly in Act Three. Attached. ) Some of these girls share similar genes because they are elated, but there the genetic similarity ends. These girls however share the same environment, a Puritan society with their self denial, their purposefulness, their suspicion of all vain pursuits, their hardhanded justice (Act One).

It is highly possible that the repression of the society leads to their behaviour, which we would term psychosomatic today. In the case of the historical references above, the people may have come from different backgrounds, but they share the same time, that is, the same circumstances, be it revolution or war, which may have caused them to act the way they did. Nature is not enough Sociology has determined that people with different genetic make-up but raised in a similar environment can more or less behave the same way. The study of sociology attempts to group people by their environment and therefore try to pick out trends.

For example, in a recent Strait Times report, boys who lack the guidance of a father are more inclined to go astray. The Economist raised this example. A gene IGF2R is found responsible for high intelligenceand children who have the variance of this gene is likely to do better in schools. But so are the children who have the benefit of a stimulating environments and sent to good schools. To be prejudiced, our group point out similarities in the Singapore educational system. Greater perecntage of students who go to top schools will eventually go to junior colleges and university than students from neighbourhood schools.

But this does not mean that these students may necessarily have the variance of IGF2R. Therefore, nature is not absolute. Nurture stands alone? We have more or less state why nature is not the sole determinant of human behaviour. But what about nurture? Evolutionary psychology do not agree with this viewpoint. It is believed that more nature allow more nurture (Evolutionary Psychology). Our existing genetic architecture allows us to respond more fully to our environment and therefore mould our behaviour. Lets use an analogy. Imagine two boys cornering you outside school, demanding for money.

If your genes make you a 1. 9 m tall and 125 kilograms worth of muscles, you will probably laugh them off, if they approach you at all. However, if your genetic architecture makes you a small sized bag of bones, you will be more inclined to either pay up or run for the nearest hiding hole. The Muscle-man and the bag-of-bones may well have the same kind of environment (eg. caring uclear family, one brother each, studying in the same school, go for the same classes and join the same clubs), but their behaviour in this scenerio will be based on their instinctive knowledge of their own genetic architecture.

There is also the idea of talents. In this aspect, we are more speculative than scientifically correct. Certain behavioural traits cannot be nurtured. Many three-year old children may have family members who play the piano at home, but not all of them are like Mozart, who started playing real pieces at that age. Perhaps a better example would be Frederic Chopin, who did not ven have an musical environment but started writing music at the age of 6. At such young ages, it is quite difficult for everything to be learned.

Some of this talent for music is probably in the genes. If behavioural genetics were around in the 18th century, the Bach family would be an interesting study, in evidence of this. A musical environment may be more likely to produce people who are musically-inclined, but it alone cannot produce geniuses. In the Bach family alone there are three internationnally renowned, respected and reverred composers: Johann Sebastian Bach and his sons Wilheim Friedemann and Johann Christian. In this case it is highly likely that genes play a part.

The effects of the environment also does not explain why some traits runs in the family. Charles Darwin, father of behaviour genetics, noted in 1872 that a gentleman had a habit of raising his arm in front of his face when sleeping and dropping it with a jerk hence hitting his nose (Darwin, C. The expression of the emotions in man and animals) This is an uncommon trait. However, years after his death, his son and daughter are also found with the same trait.

Environment cannot give a suitable explanation for this trait. It also does not explain how dentical twins who grow up apart can have the same behaviourism and why while biological children tend to behave like their parents whereas most adopted children do not. (As found by the twin study and adopted study of University of Lousiana ) Conclusion Therefore, it can be concluded that neither nature and nurture is exclusively responsible for determining human behaviour. Although genes contribute to our physical characteristics (some of which affects our behaviour) and our psychological frame of mind, our experience and education are also important in determining who and what we are.

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