What is Stephen Jay Gould's concept of exaptations as they apply to personality? Why did Gould (1991) believe that adaptation could not account for the entirety of modern human nature?
The evolutionary term exaptation was proposed by both Stephen Jay Gould, an American paleontologist and evolutionary biologist, and Elisabeth S. Vrba, a paleontolgist at Yale University, to describe functionality of traits as a result of evolution. The term exaptation stands in contrast to the term adaptation. Adaptation is used to describe traits that evolve through natural selection to serve a specific purpose, while exaptation is used to describe traits that may have evolved through natural selection to serve a specific purpose at one point but now serve a completely different function. One classic example is feathers. Feathers may have been developed at first to help regulate body temperature but later became useful in assisting in flight ("Exaptation").
The theory of evolution has also been applied to psychology in order to see how "human psychological traits" have evolved ("Evolutionary Psychology"). Personality is one psychological aspect that evolutionary psychology explores. Social scientists are fascinated by the fact that there are so many differences in human personality traits, and genetic differences can only account for some of those differences. Evolution seems to play a large role in personality differences. While some traits may have evolved as a result of adaptation, others may have evolved as a result of exaptation. One example of a personality exaptation occurring can be seen with respect to extraversion. In the article titled "The Evolution of Personality Variation in Humans and Other Animals," scholar Daniel Nettle analyzes evolution in the five factors of personality: extraversion, neuroticism, openness, conscientiousness, and agreeableness. We can look at extraversion to see how extraversion can be both an adaptation and an exaptation. According to Nettle, extraversion is a trait that can make one more "exploratory." As a result, those who are extraverts are often also more sexually exploratory and have more sex partners than introverts. We can conclude from this that extraversion can be a trait adapted by humans through natural selection in order to insure more procreation. However, those who are extraverts are also more "sensation seeking" and likely to take more physical risks. Studies show that there is a higher rate of extraverts who are hospitalized "due to accident or illness" than introverts (p. 625). The high rate of hospitalized extraverts shows us that though extraversion could have been an adaptation through the evolutionary process of natural selection to ensure procreation, it can now be seen as an exaptation because extraversion no longer serves the primary purpose of procreation but can instead be used in other various ways, often dangerous.