Our personality and the way we live our lives are not determined by either our genes or our environment, but by the interaction of both. Genes and environment each play an important role, and their complex interactions have a profound effect on our personality and nature.
Is our personality something we are born with or something we make? If we were asked this question as children, we might have answered something like this. “I’m timid because I have blood type A.” We know this is no longer true, but perhaps we’ve been trying to find the origins of our personality since childhood. So where do we look for them? When and where did our personality and way of life emerge? What governs our lives? Countless scientists and philosophers from the East to the West have explored and debated these questions, but they have yet to come up with a clear answer.
Some argue that human nature is already determined when we are born. In China, Mencius believed that human nature is inherently good, while Sun Tzu believed that human nature is inherently evil. While they seem to argue diametrically opposed views, they have something in common in that they both believe that our nature is determined at birth. While they may not have had the idea of genes in mind, their arguments are in line with what modern scientists call genetic determinism. Genetic determinism is the theory that human social behavior is determined by genes.
Dr. Thomas J. Bouchard Jr. of the Department of Psychology at the University of Minnesota studied twins who were adopted shortly after birth and raised in different households. He found that the twins were very similar in their behaviors, habits, and hobbies, even though they had been raised in completely different environments for 40 years. The Seoul National University Medical Research Center also studied 765 pairs of identical and fraternal twins and found that identical twins who were 100% genetically identical had greater personality and behavioral similarities than fraternal twins who were only 50% identical. This suggests that genes play a big role in shaping the way we live our lives. In fact, genes have even been found to influence personality formation. Dr. Klaus-Peter Lesc of Germany found that people who are more anxious have shorter lengths of DNA in which the serotonin transporter gene on chromosome 17 is repressed, and Dr. Martin Reuter of Germany found that the COMT gene is associated with the ability to control anger. Scientists who advocate genetic determinism argue that if the Human Genome Project identifies all of our genetic traits, we will be able to define our personality.
Conversely, others argue that a person’s personality and way of life is determined by the environment in which they are born. The Chinese thinker Zhuangzi argued that human nature is neither good nor evil, which is in line with the blank slate theory of the British empiricist philosopher John Locke. According to Locke, humans are born with minds that are like white sheets of paper with nothing written on them.
One of their favorite examples is the story of the boy who was a wolf. If humans are born with innate humanity through genetics, as genetic determinists claim, then Wolf Boy should have shown at least some humanity, even though he was raised in the wild. However, a wolf boy who was rescued at the age of 12 exhibited behaviors that were not at all human. We can also see how environment plays an important role in shaping human personality through several TV shows. Many of the stories in these shows are about children’s personality problems, but in many cases, the cause of their violent and rebellious nature is traced back to their parents’ behavior.
Each of these theories has its own evidence and examples, but can either genes or environment fully explain the unpredictable nature of human beings? If human nature were simple enough to be explained by only one factor, we might be able to completely control either genes or environment to create the kind of human we want. If that were the case, we might be able to eliminate criminals from the world. There are many novels and movies that explore this idea. But the reality is not that simple.
I believe that we don’t fully understand human nature because it is influenced by both genes and environment. Furthermore, I believe that genes and environment interact to create more complex mechanisms. Recently, interaction models have emerged from this perspective.
In the aforementioned study of twins by the Seoul National University team, the degree to which twins’ personalities match was expressed in terms of introversion and extroversion. Identical twins measured 0.51 and fraternal twins measured 0.25, indicating not only that identical twins are twice as similar in personality as fraternal twins, but also that genes play a 50% role in personality formation. However, this is not a complete defense of genetic determinism. If 50% of personality is determined by genes, where does the other 50% come from? If even identical twins with 100% identical genes show personality differences, it means that genes alone cannot explain it. A professor at the Korean Twin Research Center says that 40 to 60 percent of individual differences in personality are shaped by genes. Other researchers have found similar results, suggesting that not only genes but also the environment play a role in personality formation.
But how do genes and environment influence each other? Psychologists believe that genes and environment interact inextricably, and there are three main models for this. The first is the “response range model,” which states that genes don’t definitively determine human nature, but rather determine a range, meaning that even if you have the same genes, the environment in which you grow up can cause differences within that range. The second is the canalization model. The stronger the canalization, the stronger the influence of genetic factors over the environment. Finally, there is the gene-environment correlation model. This model explains that there is a correlation between genetics and the environment, so that genetics plays a big role when choosing an environment and, conversely, how we react to an environment depends on our genetics.
In the same vein, scientists say that the expression of genes in our bodies depends on the environment. In addition to the work of German professors Klaus-Peter Lesc and Dr. Martin Reuter, there are many other genes that influence personality, such as those involved in curiosity, patience, and cooperation. However, even when these genes are expressed, they are not 100% responsible for personality development, and not all of them are expressed at the same time in our lives. The environment we are in and the stimuli we receive from that environment determine whether or not a gene is expressed. In scientific terms, this is called “Selective Gene Expression”. There are many genes in a cell, but not all of them are expressed, and the expression of genes is determined by factors internal to the cell or external to the environment. The COMT gene may also be involved in personality formation by affecting the secretion of neurotransmitters in the brain. These mechanisms can also influence personality formation by acquired environmental factors, just as diabetes is caused by impaired insulin secretion.
For these psychological and scientific reasons, I believe that human nature cannot be explained without the interaction between environment and genes. This interaction makes it difficult to say which is more important: good or bad genes may be the foundation of human nature, but the right environment is needed for those genes to be expressed or suppressed and manifest as personality. In the extreme case of the wolf boy I mentioned earlier, the environment he was born in was not human at all, so I think the gene that expresses the more animalistic side of humanity took center stage. The same is true for twins. Even though they have the exact same genes, their expression is different because of the different environments they are in. Conversely, even if they have completely different environments, they still share some traits because they have the same genes.
If the way we behave were solely determined by our genes, the children of murderers might all become murderers, but this horrible situation does not happen because the environment they live in can suppress that potential. Conversely, if everything is determined by the environment, then systematic environmental manipulation and learning from birth might lead to a world in which all humans lead identical lives, but this assumption is very far from reality.
As a famous professor once said, “The genes in our bodies are just blueprints.” What is the most important thing in building a building? The blueprints, of course. But no matter how good the blueprints are, if you don’t have the right environment to build the right building based on the blueprints, will you get a great result? We humans are no different. It’s hard to say which is more important: environment or genes. Instead, genes are like guidelines for human nature. It’s the environment’s job to take those guidelines and constantly interact with them to give us direction in life. Their interaction determines our nature and how we live our lives.
