Surely you’ve heard the expression “chip like wood” when one refers to a son or daughter who looks like their father or mother. Interest in scientifically studying the effect of heredity on human behavior began with Charles Darwin and his work in the mid-nineteenth century. The Origin of Species (1859).
However, the development of personality depends on many factors that are related not only to genes. For example, the American psychologist Albert Bandura (1925–2021) already in the 1960s demonstrated a strong environmental component in behavior, conditioned by imitation based on models and reference individuals.
Although it is an issue that has been overcome for many, the dilemma between genes and the environment continues to stir debate. However, this is a false dilemma, as there are data that reflect the weight of heredity and studies that emphasize the weight of the environment. The really important thing is to find out what the genetic mechanism is and how environmental influences work.
Human development appears to be dependent on the established bidirectional relationship between biological complexity and psychological organization. This includes not only genetic and neurological activity, but also interactions with the environment and with lived experience.
In this way, the way a person relates to the environment (physical and social) can determine the direction of their development right from the womb. In fact, prenatal development will depend on the interaction between the mother and the environment. Later, as a person grows, his or her brain forms new neural connections based on his experiences.
the atmosphere weighs, and much more
The reality is that it is not 100% known whether the ratio of our value system and our psychological characteristics, such as intelligence, personality and behavior, is determined by our genetic heritage and how much has to do with culture, what we have learned. The social and temporal context that surrounds and shapes us.
Australian researcher Nathan Gillespie set the importance of the weighting of heredity in the personality of humans at 60%, although he placed great emphasis on environmental factors. On the one hand, there is the shared environment, that is, everything that we absorb from our family life and which people have in common. and not shared, on the other hand, derived from personal experiences, culture and environment.
Therefore, the genes that parents share with their sons and daughters are not necessarily much more similar than those of two strangers, as the environment will determine.
Even genetically identical twin brothers display vastly different personalities. Specifically, when their character traits were scored by tests, they showed coincidences of about 40%. Among strangers, this percentage of similarity is not very low: it is about 33%.
If we take into account that each parent shares 50% genetic material with their offspring, compared to 100% of twins, we would realize the relative weight of paternal and maternal inheritance in character. This is what makes us different among some individuals and others.
Inheritance is not a harsh destiny
However, other studies with twins have shown that some personality traits are moderately heritable and can predict a variety of behaviors throughout life, including some mental disorders.
However, the fact that high heredity may exist does not mean that it cannot be modified by experience. This environmental impact should be studied taking into account the characteristics of the organism (individual considered as a unified whole) and context, which are not experienced equally by all sons and daughters.
Adoptives with a family history of psychosis, and those who grew up in a dysfunctional adoptive family environment, also have an increased risk of developing a mental spectrum disorder.
Conversely, boys and girls who grew up in families where an atmosphere of respect, responsibility, and love prevailed, with consistent rules and boundaries, showed greater emotional well-being. It favors optimal psychological development in the future and plays a protective role in the manifestation of future mental disorders.
Faced with this scenario, more holistic or comprehensive explanatory models of human development have emerged. Epigenetics fits into this context, which studies how environmental conditions can activate or deactivate the expression of certain genes without altering the genetic sequence.
This will help to understand how the presence of harmful habits in pregnancy is related to a higher risk of suffering from chronic diseases in the offspring. Or, as if it were a memory, the habits of our lives influence and result in generations to come.
Studies on the Great Chinese Famine, the so-called winter of hunger The conditions of prisoners of the Dutch or Secession War or the American Civil War have shown that the experience of these episodes left changes in the expression of certain genes – associated with aging and schizophrenia – and affecting current generations.
Today, epigenetics is playing a fundamental role in the interpretation and treatment of many diseases and mental disorders.
Therefore, the expression “chip like wood” doesn’t seem generalizable. Genetic endowment and epigenetic factors are crucial for understanding human behavior and mental health, but the environment is a very important variable. Furthermore, we must keep in mind that these external factors will not affect all people equally.