Dr. Adam Johns
English Composition 0200
15 October 2014
Lewontin and Jensen IQ Theory
An article called “Genetics and the Great IQ Controversy”, written by Bruce Wallace, states that “the environment, as well as hereditary, can effect someone’s IQ score,” (Wallace 13). “IQ scores predict with fair accuracy a person’s eventual standing in respect to occupational prestige,” (13). Wallace’s article introduces a philosopher named Arthur Jensen, who in fact generated this theory that environment and genetics play a role in your IQ score. To test his theory, he decided to use identical twins and the differences in the environments in which they live. His theory can be compared to the information Lewontin provides in the chapter, “All in the Genes?” where he describes his ideas about IQ scores. Lewontin’s and Jensen’s concepts show that not only can your environment effect your IQ score but even genetics can as well.
Lewontin and Jensen both thought that using twins would be a prime example for this theory. Lewontin’s use of twins sparked an idea that “if twins are more similar than ordinary sibs or if twins raised in completely isolated families are still similar, then this surely must be evidence for genes,” (Lewontin 32). Lewontin was very intrigued and decided to use identical twins rather than fraternal twins due to the fact that identical twins share 100% DNA whereas fraternal twins only share 50% DNA. Both Lewontin and Jensen had the same approach on testing the effect of the environment by comparing data from identical twins living together and data from identical twins living apart. Essentially, they took identical twins and separated them so they were not living with their biological parents. “As a result of the studies, Jensen found that about 80% of the observed variance in IQ scores has a genetic basis, and the remaining 20% is caused by environment,” (Wallace 13). In other words, the results showed that the environment in which the twins lived did have an effect on the scores, but rather their genetics had a bigger effect.
Lewontin wanted to expand on this test and take it one step further by researching ordinary adoptive children. He wanted to expand on Jensen’s hypothesis by seeing “if adopted children resemble their biological parents more closely than they resemble their adoptive parents […],” (Lewontin 33). While testing this, he found that the adopted child’s IQ score resembled the biological parents IQ score, which indicated that genetics plays a role in IQ scores. Furthermore, into the study, he found that the longer the adoptive child lived with their adoptive parents, the child’s IQ score was significantly higher than their biological parents. This test also showed that “the average IQ scores of these adopted children were about equal to the IQ scores of the adoptive parents,” (34). So essentially, the adoptive child had an IQ score that was very similar to its biological parents score, but after living with the adoptive parents, the child’s score increased even more. From these results, it’s safe to say that the environment and the genetics played a significant role in the higher IQ score of the adoptive child living with their adoptive parents.
Now the results from this tests does not mean that if you get adopted than you are going to have a very high IQ score. Moreover, it simply means that most people who can adopt children “are usually middle-class and have an appropriate education and cultural experience for the content and intent of IQ tests,” (35). Also, people who typically put their children up for adoption are either too young, not financially stable, or unemployed, so it would make sense that the adoptive parents would have a much higher IQ score than the biological parents. Furthermore, the biggest factor that influenced higher IQ scores were the living conditions the adoptive parents raised their children, which would be a healthy, safe, educational environment.
By using both the results of the tests, identical twins and the adoptive child, you can conclude that genetics and environment can play a huge role in achieving a higher IQ score. So essentially, both Jensen and Lewontin are correct in the fact that environment and your genetic background can play a significant role on your IQ scores.
Lewontin, Richard C. Biology as Ideology: The Doctrine of DNA. New York, NY: HarperPerennial, 1992. Print.
Wallace, Bruce. "Genetics and the Great IQ Controversy." Genetics and the Great IQ Controversy 37.1 (1975): n. pag. Web.