In this blog post, we will look at whether human personality and behavior are determined by heredity or by the environment from a scientific perspective.
Edison’s saying, “Genius is 1% inspiration and 99% perspiration,” is a very famous aphorism. In fact, Edison is said to have said this to emphasize the importance of 1% inspiration, but many people take it to mean that hard work is very important to succeed. If so, then it is necessary to consider whether Edison’s original intention is correct from a scientific point of view, or whether the meaning that people currently accept is more appropriate. This is related to the question of whether human personality or abilities are innate or acquired.
Even before the gene was discovered, there were various theories about the formation of human personality. Some believe that the environment is important for a person’s growth, while others emphasize the importance of heredity, as in the saying “a son resembles his father.” The fact that both views have coexisted for so long is because there are various examples that prove each view.
First, environmental determinists, who argue that the environment plays a key role in determining personality, offer the following evidence. For example, even identical twins who are genetically identical, but raised in different environments, do not have 100% identical personalities or abilities. In fact, one study found that when one of identical twins is gay, the other twin has a 50% chance of being gay. Another study found that only one of identical twins has the genetic disease ‘Russell Silver Syndrome’. If genes unconditionally determined personality or health, these cases would not occur. Therefore, environmental determinists argue that individual tendencies or health are not dependent on genes, and that personality or tendencies can be changed through psychotherapy or a new environment.
However, there are also examples that contradict these claims. For example, there are cases where twins who were adopted separately as children meet 40 years later and both become weightlifters, or cases where, despite growing up in different environments, they have almost the same favorite subjects, smoking and drinking habits. From the standpoint that environment determines everything, it is difficult to explain such cases as mere coincidence. Even if the probability of being homosexual is not 100%, there is no denying that there is a certain degree of correlation.
On the other hand, there are also genetic determinists who argue that genes play an important role in determining human personality and behavior. This is a relatively new argument that has gained strength as the structure of human genes has been revealed. Genetic determinists argue that personality and behavior are determined by genes, citing the counterexamples of environmental determinism mentioned earlier. They say that the fact that identical twins have the same occupations, hobbies, and drinking habits is not a coincidence but an inevitable result of their genes.
The claim that genes determine human tendencies is supported by research on the MAOA gene. Han Brunner of the Netherlands found that if the MAOA gene is short, it causes problems in controlling anger and leads to violence. This means that the short MAOA gene is a gene that symbolizes violence. Furthermore, Richard Dawkins, in his book The Selfish Gene, argues that humans are just tools used by genes to thrive, and that all human behavior is according to the program of genes.
However, the number of genes is smaller than expected, raising questions about the claim that all behavior is determined by genes. It has been found that humans have about 20,000 genes, but this number alone does not seem to be enough to explain all human characteristics. In addition, the fact that identical twins can have different genetic diseases shows the limitations of genetic determinism. The claim that genes completely determine human behavior denies an individual’s free will and raises ethical issues of treating them as potential criminals or patients.
Epigenetics is a discipline that aims to solve these problems. Epigenetics claims that the same gene can have different expressions depending on whether it is expressed or not, which can lead to different personalities and behaviors. For example, the genes of a worker bee and a queen bee are identical, but the gene that makes a bee a queen is expressed by an external factor called royal jelly. This can be seen as a position that encompasses both genetic determinism and environmental determinism.
In the end, it can be said that both the environment and genes influence human behavior, but genes play a more important role. The fact that identical twins do not have 100% identical traits is only a matter of gene expression, and if the expression conditions are met, they are likely to show the same tendency. Even if the number of genes is small, the complexity is sufficient when considering the possibility that each gene will be expressed.
Therefore, if the mechanism of gene expression is revealed, ethical issues can be solved to some extent. Simply the existence of a gene cannot be used to label someone as a violent person, and if a way to block gene expression is found, potential problems can be prevented.
In conclusion, genes have the greatest influence on human behavior. Although the roles and expression conditions of each gene have not yet been fully elucidated, as soon as these are clearly identified, we will have a deeper understanding of the nature of humans. As such, Edison’s maxim, “Genius is 1% inspiration and 99% perspiration,” can be interpreted in the sense of considering both genes and expression conditions.
