20117 이준우 Refutation and Concession

1. What is my thesis?
I think that Nurture plays more important role in shaping human behavior and characteristic.
2. What is the opposite position?
Nature is more important than nurture in shaping human behavior and characteristic.
3. What arguments can I anticipate?
Twins studies showing a strong IQ correlation between identical twins.
4. How will I counter those arguments?
It is not only nature but also nurture.

Counterpoising genetics and environmental influences is somewhat misleading, despite the partisan claims of people on each side. Many human traits and behaviors result from both genetic and environmental factors. Moreover, genetic and environmental influences on a trait are not simply additive. Genes “interact” with the environment. That is, genes provide the potential for a trait, but environmental conditions determine whether that potential will be realized. The same genetic codes may be expressed at different levels in different environments. Compare, for example, Asian immigrants in the United States to U.S.–born Asian Americans. U.S.–born Asians are twice as likely as immigrants to suffer from prostate cancer, and Asian-American adolescents born in the United States are more than twice as likely to be obese as Asian-American adolescents who recently immigrated to the United States. U.S.–born Asians and immigrant Asians are likely to have similar genetic predispositions for prostate cancer and obesity. The differences between the two groups in the prevalence of these disorders are, therefore, likely to be caused by environmental conditions such as lifestyle and diet. To understand gene-byenvironment
interactions, we must evaluate the estimated heritability of traits in particular environments. The term heritability is often misunderstood. The traditional twin study design generally produces a single heritability estimate. Heritability, however, is not a fixed property of a trait; it could vary from one population to another. For example, under different social circumstances, the heritability for cognitive development may differ. We could make one estimate of heritability based on a U.S. middle-class population and another based on a low-caste population in India. We would expect the former to be significantly larger than the latter. In a modern liberal democracy, individuals enjoy more access to educational opportunities than in a traditional aristocratic society. As a result, the differences in cognitive achievement in a modern democracy should be due more to genetic differences than in a traditional society. An egalitarian, democratic society can be thought of as a “normal” environment for estimating the heritability of cognitive development, where the “genetic potential” for cognitive development can be realized. We can compare heritability in a traditional or more hierarchical society against this potential.