Behavioral Genetics: Nature vs Nurture.

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Sir Francis Galton started the debate nature vs nurture in 1869. One hundred and forty six years later the debate continues and no clear conclusions have been reached; are people determined by nature or shaped by how they were nurtured? I believe that the family you are born into, as well as the way you are nurtured, influences and shapes your behaviour and personality. To clarify, nature acts to shape the nurtures personality and behaviour; therefore, one is shaped by nature. Through personal experiences I will illustrate the aforementioned claim of nature’s role in nurture.

“The Minnesota Twin Family Study” was a study conducted by Thomas Bouchard at the University of Minnesota from the years 1979 to 1999. Bouchard’s experiment examined identical and fraternal twins of the same gender that were separated at an early age. Bouchards’ experiment concludes that although the twins were not nurtured by the same person or raised in the same environment, they possessed great amount of similarities. To exemplify, the results indicated that some twins had the same dental hygiene discipline, while other twins had the same hair style, some twins liked the same movies while others liked the same music. The study also found that “genetics account for 50% of the religiously among the population – in other words, both identical twins raised apart were either likely to be religious or not to be religious, compared with unrelated individuals.” (Segal, 256). The findings indicate that the religion is identical among the fraternal and identical twins. I believe that the results of this research are astonishing. The probability of similarity amongst two people raised in different environment is rather uncommon. Identical twins are the result of fertilized egg duplicating itself with the ‘exact same genetic material’. Even when the nurturing environment were significantly different, the identical twins had similar traits. This clear evidence proves that nature overpowers nurture and sometimes our traits are not within our control.

Preference of sexuality is a similar debate in that research indicates a relationship between nature and sexuality. When we look at different cultures and societies it is fair to say that most parents in these certain cultures nurture their kids in believing that being gay is socially unacceptable. Yet despite of social expectations, the gay-oriented community compromises a significant fraction of present day society.  In a recent study, 40 pairs of gay brothers were examined by psychologists. A thorough study concluded that: “The pairs of brothers shared the same markers at an above-chance rate in just one region of the X chromosome, a region named Xq28, which lies near the tip of the long arm of the chromosome. This was interpreted to mean that a gene or genes predisposing to homosexuality lay in that region.”(LeVay, 171). The results of the study indicate that a “gay gene” does in fact exist and is structured deep within our biological nature. In another study, LeVay found that the hypothalamus in gay men was smaller. The hypothalamus, which is a part in the brain has many functions but in relation to sexual orientation it governs moods, sexual drive and the release of hormones in the body.  LeVay concludes the study with the following statement: “The cluster of neurons known as INAH 3 in the hypothalamus were reduced in size in homosexual men, much to the same degree that the same group of neurons is reduced in women.” (212-213). Estrogen and testosterone are the sexual hormones in women and men, respectively.  Testosterone is classified as a male hormone that is also found in women and a smaller hypothalamus could mean that less testosterone is being produced which may give men female-like traits. This clearly indicates that there is a change in the chemistry of the brain which means that these feelings are out of our control and nurture has little affect ones nature.

Using the IQ test as an example: “The research indicates that identical twins raised apart are about 80% percent alike on the IQ tests… Fraternal twins are less than 50… me and a random person are 1%.” (Perspectives in Psychiatric Care, 88-94). Probability indicates that a randomly selected person in a sample size of 100 people have a lower IQ level with respect to a same study amongst identical twins. If we were to suppose that genes had no effect on an individual’s IQ level, the probability for 80% of the people to have the same IQ level, by sheer luck, would be .0008%. That’s 1 in 125,000 people. It is therefore almost improbable for a statistic of 80% to be a mere coincidence in results.  “The Minnesota Twin Family Study” also found that when comparing the IQ level of adopted kids and their adoptees there is no correlation. The results of the comparison were as if comparing the adopted kids to complete strangers. The adopted kids are learning and mirroring their adoptees and yet if it is in their genes they will surpass them, vice-versa.

Many personality traits have proven to be gene related. As found in “The Minnesota Twin Family Study”, many twins even after being raised apart had many similar personality trait. Some had the same sense of humor while others were either socially incompetent or “social butterflies”. These we see not only amongst identical twins but amongst parents and extended family members. I noticed that I have many of my parent’s traits. I like that have my mother’s thinking process and my father’s entrepreneurial skills. Conversely, I dislike that I have my father’s short temper which he would have inherited from my grandfather who also had a short temper. When I went to visit my family in Albania in 2013, I noticed the exact trait amongst my extended family, particularly in my dad’s nephews. My dad and his seven brothers were born and nurtured by the same parents so it only make sense that the brothers have similar tempers and thus traits. Furthermore, I noticed the way the kids spoke to their parents. My first cousins spoke back to the parents the exact same way as I did despite the fact that we were raised in two completely environments.

In conclusion in the debate nature vs. nurture there are strong evidences that nature shapes nurture’s personality and behaviour. When identical twins are raised apart they have many similar traits. People are born gay, they don’t became gay. The IQ level of an adopted child is the same as a stranger in comparison to his adopted parents. A Neuroscience approach is most logical in explaining the side of the views of the debate. It appears that in an uncommon way our destiny has been written for us within our genes. It doesn’t matter where we are born and raised and how far we run because no matter how hard we try we cannot escape our biological structure (genes) and the fate that they hold for us.


Works Cited


LeVay, Simon. Gay, Straight, And The Reason Why : The Science Of Sexual Orientation. Oxford:

Oxford University Press, 2011. eBook Academic Collection (EBSCOhost). Web. 12 Mar. 2015.


LeVay, Simon. Queer Science the Use and Abuse of Research into Homosexuality. Cambridge, Mass.: MIT, 1996. Print.


Keltner, N. L., James, C.A., Darling, R.J. Findley, L. S., & Oliver, K. (July-September 2001).

Nature vs. nurture: Two brothers with schizophrenia. Perspectives in Psychiatric Care, 37  (3), 88-94. (Academic Search Complete)


Segal, Nancy L. Born Together–Reared Apart : The Landmark Minnesota Twin Study. Cambridge, Mass:      Harvard University Press, 2012. eBook Academic Collection (EBSCOhost). Web. 12 Mar. 2015