The human body is the result of millions of years of evolution of the material found in the nucleus of cells: DNA. Genes are the units of information that this genetic material possesses , and the translation of the genetic code is expressed in characteristics, whether physical (the colour of the eyes, the type of hair or the shape of the nose) or psychological (behaviour or personality).

But does everything depend solely on the genes? That is, are we what we are and do we behave the way we do because our DNA says we are? The answer is no. The environment around us has something to say about that. Human nature is very complicated, but we are getting closer to understanding it every day.

Genetically based behavior

Using twins for studies has been a great tool that scientists have used for years to understand how genes and environment influence each person differently. The idea is to look at the extent to which it is the upbringing or genes that serve to better predict the regularities that can be found in the body’s development and repertoire of habitual behaviors.

Twin research shows great evidence of when and how genes and environment shape human nature. Some of them reveal that the importance of genes can change dramatically depending on the stage of life we are in. Genetic influence tends to increase over the years in many characteristics s, as seen with body weight.

In another area, research with twins has been important in the field of molecular genetics. The best known is with body weight. Thanks to this kind of study, it has been possible to identify almost 100 genetic variants involved in obesity.

But the effect of genes does not have to be limited only to how our body is formed; also explains how certain psychological predispositions appear . For example, it is believed that we make choices in search of an environment that favours our predisposition to express genetically inherited strengths. A teenager who is genetically good at reading will probably start going to a library to look for more books, where he will meet people who think similarly to him and may start to relate to them.

Similarly, IQ is largely inherited and it is difficult to change it in a meaningful and sustained way through exercises and new learning.

Fear of genetic determinism

Twin studies are a great opportunity to understand when the environment is stronger on us and when behavior is easier to shape.

However, in the field of psychology and cognitive sciences, have been involved in the controversy . Critics of twin research question whether psychological characteristics, such as mental health, have a strong genetic basis. This is due in part to a fear that everything we think, feel, and do is little more than the consequence of genes doing their job and condemning us to a life we cannot change.

However, this fear is unfounded.

Genes are not everything

The influence that genetics has on human characteristics is often misunderstood . It is wrong to assume that behaviour that has a strong genetic influence must be innate by obligation. Genes are not everything; a gene will be expressed depending on the environment, that is, it may show its effects or directly have none, depending on the environment in which we live.

An example will make it clearer. There are people who are predisposed to lung cancer because of their genetics. Unless they smoke or breathe tobacco smoke constantly, they are unlikely to develop the disease. And this is being seen with behavior. The behaviour is obtained as a response to an environmental signal .

Although some forms of behavior have a genetic basis, this does not imply that this predisposition will cause our brain to be designed to manifest these behaviors regardless of how we interact with the environment. Although our DNA cannot be modified through experience and learning, the expression or not of its genes depends largely on the environmental conditions in which we live. For example, studies in relation to schizophrenia (a mental illness with a strongly genetically inherited component) show that the expression of the illness is higher when we live in a context that produces stress.

Does knowing the genetic basis imply danger?

One of the fears generated by this work is that, by recognizing that behavior has a genetic basis, people will cease to be equally responsible for committing themselves to healthy behaviors and to the education of their children.

However, knowing one’s predisposition to suffer from a mental illness or other types of illness does not necessarily lead to a loss of interest in improving health; on the contrary, one gains a commitment and motivation to change one’s behaviour and habits .