The Halcyonite

by: Zephyr K. (Grade 10)

One of the oldest and most fiercely contested scientific questions is the ‘Nature vs. Nurture’ debate, which spans the fields of both psychology and biology. It discusses whether human behaviour is more heavily determined by external influences during a person’s life, or a predestined framework set out by genes. The term was first coined in 1869 by polymath Francis Galton, a eugenicist fascinated by the idea of ‘race improvement’; but the concept itself was discussed centuries before by Greek philosophers, such as Plato and Aristotle. Today, it is widely understood that viewing these two influences as entirely dichotomous is both potentially dangerous and biologically implausible. The belief that differing social outcomes are caused by inherent strengths or flaws has triggered the promotion of horrific acts, such as sterilisation and genocide. It is also important to recognise the role of genes in the inheritance of health problems so that they can be predicted and prevented. Neglecting either facet of the question also restricts our ability to explore the interactions between environmental and genetic factors. However, we must first explore the proof used to justify both stances in order to understand their interdependence. 

There is a range of environmental influences that have been shown to affect human behaviour. These are (generally) the most impactful during childhood, given that major developmental processes are taking place at this time. For instance, a study at the University of Pennsylvania has shown that the mental stimulation that a child receives at the age of four is instrumental in determining the development of language and cognition skills. Researchers monitored the books, toys and instruments the participants had access to. When the participants were between the ages of seventeen and nineteen, brain scans revealed that those who had received more stimuli had more developed cortices. The most clearly affected region of the brain was the lateral left temporal cortex, which is responsible for semantic knowledge, such as vocabulary. 

Negative external influences can also have a powerful impact on children. Young people growing up in impoverished communities are far more likely to witness acts of violence. Issues triggered by exposure to these traumatic events can include: a decline in school performance, symptoms of anxiety, and an increased risk of substance abuse. However, mitigating factors, such as positive relationships with family or a space to discuss experiences, have been shown to decrease the likelihood of children developing these problems. 

Additionally, some geneticists argue that the most impactful external influences are unpredictable and unsystematic, so that they are more difficult to plan for or prevent. Yet equally those that can be regulated and systematised, such as the role of diet in health, can still be adversely affected by underlying genetic conditions – for instance, genetic predispositions affecting weight loss and weight maintenance – so nurture can go only so far.

Heredity affects our behaviours and tendencies in a range of ways. Twin studies are considered by many to be conclusive evidence that genetics are the predominant factor in how humans develop. Between 1980 and 2000, the University of Minnesota studied 81 identical twins. Arguably, the most notorious of these experiments were Jim Lewis and Jim Springer, who were raised apart until the age of 39. Both men were prone to tension headaches, smoked the same brand of cigarettes and even drove the same car. These studies were also used to examine the heritability of IQ. This led to the discovery of the Wilson Effect, which demonstrated that the correlation between genes and intelligence increases with age. As one becomes older, their IQ remains much more constant. This suggests that despite spikes and stalls in development during childhood, IQ seems to revert to a genetically predetermined trajectory. While cases of naturalistic IQ change were observed, they occurred at a range of different ages, and did not seem to have any common causation. 

However, some dispute these results as irrelevant, as many experts do not believe that IQ tests are an accurate measure of intelligence. It is also argued that twin studies are based on the false assumption that monozygotic (identical) twins share exactly the same DNA. In fact, identical twins are believed to differ by an average of five genetic mutations.

While most genetic predispositions are understood to be the effects of multiple genes interacting, there are some instances in which a single mutation can have a significant impact. For instance, when the MAOA gene located on the X chromosome is defective, it can be associated with higher levels of aggression. People with this mutation have lower levels of dopamine and serotonin, which can cause an inclination towards violence and antisocial behaviours. A study in 2008 showed that a specific variant of this gene was associated with severe aggression in boys aged between twelve and eighteen.

Epigenetics, the study of how external influences affect gene expression, has begun to unravel the mystery of how the forces of nature and nurture interact. Factors such as stress, nutrition, and exposure to toxins can affect which genes are turned “on” or “off”.  As this field is relatively new, most of the studies available are based on animal models,  but scientists are confident that this information can be used for the benefit of humans. For instance, it has been shown that a ketogenic (high fat and low carb) diet could help people suffering from an intellectual disability called Kabuki Syndrome. Individuals with this disorder possess a mutation of  the gene KMT2D or KDM6A, hindering the  transcription of genetic material, which affects memory and motor skills. Ketones, which are produced by the breakdown of fat, may help to inhibit this mutation.  A team of researchers at McGill University also discovered that when rat pups were groomed by their mothers, certain genes were activated that caused the production of stress-moderating proteins.  

A resolution to the debate of Nature vs. Nurture would be ideal, but modern science demonstrates that there is a nuanced and sometimes unfathomable equilibrium between the two that we are still striving to understand.

Do you have an opinion in regards to this debate? Leave it in the comments below!