221782401-Evolution and Behavioral Genetics

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Evolution and behavioral genetics are often discussed to be a part of why humans are the way they are today. Based on what people know about human evolution, many of our behaviors are learned from our ancestors to increase our chances of survival. According to Tooby and Cosmides (1990), because of the nature of the evolutionary process that creates this interaction, “genes” and “environment” exists in a highly structured relationship that is very different from popular conceptions of separate but parallel genetic and environmental “influences” (p. 20). We learn that evolution acts through genes, but it also acts on the relationship between the genes and the environment (Tooby & Cosmides, 1990). There are often misunderstandings that surround the biological study of behavior and personality. According to Buss (1990), one is that there is a biological perspective—a single, unified, monolithic approach. This views errs for two reasons a) There are several distinct levels of biological analysis (e.g. evolutionary, behavioral genetic, psychophysiological), each with distinct theoretical assumptions, content, and methods, and b) within each level, there are often competing theories about the same set of observations. Biological approaches to personality are many and varied, not singular in nature (p. 3). Another common misunderstanding is that biological approaches are somehow at odds with approaches that are considered “environmental” or “social” (Buss, 1990). Many biological approaches, particularly those that are evolutionary, focus precisely on how organisms deal with their environments (Buss, 1990). As one biologist aptly put it, “The whole reason for phenotypes’ having evolved is that they provide flexibility in meeting environmental contingencies” (Alexander, 1979, p. 14). Evolutionary approaches are not opposed to environmental approaches, they describe how, through a long history of natural selection, environments have shaped organisms to adapt strategically to their environments (Buss, 1990).

When looking at human behavior, it is possible to conclude that much of human behavior is the product of the environment. According to Tooby and Cosmides (1990), both the psychological universals that constitute human nature and the genetic differences that contribute to individual variation are the product of the evolutionary process, and personality psychology must therefore be made consistent with the principles of evolutionary biology (p. 21). This means that every personality phenomenon is, from an evolutionary perspective, analyzable as either (a) an adaptation, (b) an incidental by-product of an adaptation, (c) the product of noise in the system, or (d) some combination of these (Tooby & Cosmides, 1990). Developmental programs are directed by the genes, but they require and depend upon an entire range of properties of the environment being reliably and stably present in order to successfully produce a healthy individual (Tooby & Cosmides, 1990). Therefore, if the environment and genes are being shifted and changes, the result of the individual will change as well. No organism reacts to every aspect of the environment. Instead, the developmental programs rely on and interact with only certain defined subsets of properties of the environment, while others are ignored (Tooby & Cosmides, 1990). As an illustration of this, a cat is able to mate with another cat to reproduce but would not be able to reproduce with a dog.

According to Plomin and Nesselroade (1990), although environmental factors leap to mind when we think about change, change cannot be ascribed a priori to the environment because genetics can contribute to developmental change (p. 195). Evolution and behavioral genetics is explored by conducting studies to see how genetics affect social attitudes, extraversion, neuroticism, and psychoticism (Eysenck, 1990). One of the studies published by H.J. Eysenck and Gudjonsson (1990) involves research that criminality or generally antisocial behavior is correlated to each other. This research study was carried onto different countries such as India, Germany, and the United States (Eysenck, 1990). The first studies show the concordance for criminal behavior is much greater for MZ twins than DZ twins (Eysenck, 1990). The second line of evidence shows that the criminality of adopted children is determined to be very significant by the criminality of their true parents (Eysenck, 1990). The heritability of criminal conduct is estimated to be about the same level as the estimates of heritability found for personality. Therefore, combinations of personality traits can be shown to issue in social conduct which is very significantly influenced by genetic factors (Eysenck, 1990).

In addition to how evolution and behavioral genetics can influence one’s violent behavior, analyses have been done on impulsive, sensation-seeking behavior, and aggression (Zuckerman, 1990). Sensation seeking has been defined as a human trait characterized by the need for “varied, novel, and complex sensations and experience and the willingness to take physical and social risks for the sake of such experience” (Zuckerman, 1979, p. 10). From this, it is suggested that sensation seeking is a trait that has evolved as a function of its adaptive value for survival and reproductive fitness (Zuckerman, 1990). A sensation seeker from our hominid ancestors was probably more exploratory and adventurous than the sensation avoider (Zuckerman, 1990). Using this ability of trait, it helped our ancestors increase their access to food sources and mates.

According to Zuckerman’s study (1990), while many of the correlations are not high, they do suggest some relationship of sensation seeking to the monoamine systems regulated by MAO in the brain the noradrenergic, dopaminergic, and serotonergic ones (p. 317). Studies conducted to explore the MAO levels in the brain and how environment affects an individual allows us to explore how these factors play a big role in behavioral genetics.


In a recent news article from CNN entitled “Accused Killer says he killed Ohio couple in ‘77” (Falcon, 2010), Edward W. Edwards is a 76 year old man who wrote about his life as a career criminal in his autobiography. Edwards’ autobiography was written in 1972, and it discussed about his criminal activities which included arson, robbery, and theft. One of the criminal activities he wrote about confessed to killing a young couple 33 years ago. How could he have killed this young couple many years ago and be able to get away with it?

Studies of evolution and behavioral genetics show that although we are born with genes, our genes are also affected by our environment. It is possible that Edwards was raised in an environment that caused him to be disturbed and resulting in having anti-personality disorder. Since behavioral genetics can affect one’s violent behavior, Edwards probably committed these acts as a way to fulfill his sensation-seeking behavior. Although it may be immoral to us to be able to murder others, Edwards probably enjoyed the thrill of the situation when acting in his crimes.

As stated earlier, our ancestral sensation seekers probably sought adventures and experience as they explored their curious mind. It helped them survive because being a sensation seeker could increase their chances of gaining food sources and mates. In Edwards’ case, his need for sensation seeking was probably used for him to fill in a void he may have had in his life. Another possibility to why Edwards would commit these crimes is that he was probably born with genes that cause him to be more violent with a more introvert personality. He may have not had many close friends or people around him, which is how it is an example that genetics can affect one’s social attitudes, extraversion, and neuroticism.

Since sensation seeking is also affected by one’s MAO (monoamine oxidase) levels. MAO is an enzyme in many cells that can affect the levels of epinephrine, serotonin, and etc. When a person, like Edwards, does not have a balanced level of brain chemicals it can alter the reactions of how one responds to situations. By combining the factors of the environment and biological genes that a person is living with, social and physical risks can be considered for experience. Thus, evolution and behavioral genetics can explain how conflicts and aggression may arise in the example of Edwards.


So how do we explain the mass killings at Columbine High School with evolution and behavioral genetics? It is a possibility that the environment and genes of Harris and Klebold were changing and shifting, which may cause their behavior to change. Some say that the boys’ intentions were not to have a school shooting, but actually wanted to bomb their school in order to be more infamous than Oklahoma City bomber Timothy McVeigh (Chen, 2009). The Columbine tragedy left a lasting mark on many people, but the knowledge that most people thought they knew about the shooting is actually filled with misconceptions (Chen, 2009). People perceived Harris and Klebold as a couple of kids that were a part of the “trenchcoat mafia” and was trying to get revenge on the jocks that were bullying them, but they were actually not affiliated with them (Chem, 2009). Many people still do not know the actual facts to this incident, but psychologists studying this incident finds that these boys are actually not who majority of people think they are.

Evolution and behavioral genetics says that much of human behavior is caused by adapting to the environment, but also affected by genetics. If this is true, then it means that Harris and Klebold’s behavior of violence may have happened because of their biological and environmental circumstances that they were surrounded with. In recent findings, we notice that these boys were actually not complete social outcasts (Chan, 2009). If the incident did not occur to seek revenge from being “bullied”, then based on the other reason of how evolution and behavioral genetics can apply to their behavior, it is probable for them to also feel the need for sensation seeking. They were probably bored of their life and wanted to seek some sort of excitement and attention. It was noted that Harris was a psychopath and Klebold battled depression (Chan, 2009). This can also relate to a possibility that the boys’ brain levels of MAO were not necessarily balanced. Since genetics affect one’s psychoticism, extraversion, and many other types of personality traits, it may be hard to change these things that could be genetically given to them. Knowing that biology and environment play a major role with each other, we can reduce certain violent behaviors by enforcing a better environment for a person but genetics may still change the outcome.


Buss, D.M. (1990). Toward a Biologically informed psychology of personality. Journal of Personality, 58, 1-16.

Chen, S. (2009). Debunking the myths of Columbine, 10 years later. Retrieved April 5th, 2010 from cnn.com: http://www.cnn.com/2009/CRIME/04/20/columbine.myths/

Eysenck, H.J. (1990). Genetic and environmental contributions to individual differences: the three major dimensions of personality. Journal of Personality, 58, 245-261.

Falcon, G. (2010). Accused killer says he killed Ohio couple in ’77. Retrieved May 4th, 2010 from cnn.com: http://www.cnn.com/2010/CRIME/05/04/ohio.slayings.confession/index.html?npt=NP1

Ploman, R. & Nesselroade, J.R. (1990). Behavorial Genetics and Personality Change. Journal of Personality, 58, 191-220.

Tooby, J. & Cosmides, L. (1990). On the Universality of Human Nature and the Uniqueness of the Individual: The Role of Genetics and Adaptation. Journal of Personality, 58, 17-67.

Zuckerman, M. (1990). The Psychophysiology of sensation seeking. Journal of Personality, 58,313-345.

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