The Contextually Dependent Brain Part 2

Understanding Nature vs Nurture Through Genetics: Part 2

There are many ways that the environment plays a role in development and even the genetic level is not immune to its effects. Because environments are so complex, contain many moving parts, and are near impossible to control, they are not as easy to study and understand as one might hope. However, there is a lot that we have learnt. In genetic and biological development, there is very much an environmental scaffolding. This means that at every stage of development right from the beginning, the environment plays a role in how things proceed. Remember how in the previous piece I mentioned that there is a genetic manual? That manual carries detailed instructions, but whether that gets expressed and how it gets expressed are very much dependent on the environment.

Remember how in Issue 1, Part 4, I discussed how a person is always to be understood as a person in context? How they are constantly acting on (influencing) their environment and their environment is acting on (influencing) them. Genetics and nature vs nurture gives us a biological perspective of this as well.

Internal Environment vs External Environment

Now, when I speak of the environment, it's important to differentiate between two types of environments. In all my pieces, when I speak about the environment, I am nearly always speaking about the external environment. However, when we speak about genetics, it's important to understand that geneticists often mean something completely different by environment. They are referring to an internal environment.

An internal environment can mean something as small as the conditions within a cell in the body which contains a particular gene or protein. It can mean the context of what is happening within the body at even the molecular level. An external environment is everything that happens outside of the body and outside of the biological. It can be a home environment, the environment of the mother's womb, the natural environment (like clean air, water, plants, etc.).

There is a constant interaction between the internal and external environment. Both these environments are dynamic and constantly changing. For example, a woman who consumes alcohol (external environment) or is exposed to a harmful environment with toxic chemicals (external environment) while she is pregnant can affect the baby at the genetic, cellular, and biological levels (internal environments). This effect will drastically change how the genes function and how the body develops.

Epigenetics

All these matters about genes changing and being dependent on the environment is a field of study called epigenetics. Epigenetics is a fascinating topic. It’s a relatively new and rapidly developing field in genetics which is concerned with how genes can change the way they function over time in response to the internal or external environment. Epigenetics helps us to understand the magnitude of the environment's effect on child development at the biological level. These changes, or the way the gene functions, is called “gene expression” and can happen throughout the lifetime, before and after birth.

Geneticists used to believe that epigenetic changes happened over time across multiple generations, but they have come to see that these changes can happen in a transmission directly from parent to child (i.e. within a single generation). This leads to the conclusion that the environment of the parent can fundamentally affect how the child develops even before they are born, possibly even before the mother herself is pregnant, but also, after they are born.

There are three levels to epigenetics which I would like to discuss. The first is where environmental factors affect the child’s DNA and change it (Purely Environment). The second is where the environment “triggers” or “switches on/off” something that the individual was genetically predisposed to (Gene x Environment Interaction). The last level is where someone's genetics lead them to seek out certain environments (Gene-Environment Correlation).

Environmental factors only:

This is where the environment that an individual grows up fundamentally affects their genetics. Factors from the child’s external environment affect them, and this can be before or after birth. These are factors like where a mother was chronically depressed, stressed, or on drugs while she was pregnant. This affects the baby's biological development right at the gene level, changing how the child’s genes are expressed.

This means that even if genetically, the child was going to be typical (“normal”) with no issues, they have now mutated the child’s genes to behave a certain, disordered way. This comes in things like physical development, that the body or brain does not develop well. In another way, environmental factors could be that the child's body develops to be able to adapt to certain environmental conditions like extremely hot or cold weather or chronically stressful environments.

Gene x Environment Interaction - Switching genes on and off:

This is where the child might be genetically predisposed to something (so, for example, if alcoholism or mental disorder like schizophrenia runs in their family), but something in their environment either blocks or triggers the expression of that gene. In this way, the interaction of the gene and the environment is more effective than just the gene or just the environment on its own.

For example, if someone comes from a family that is genetically predisposed to alcoholism, they are more likely to become an alcoholic than someone who is not genetically predisposed. But most times, whether they become an alcoholic or not depends on the environment. If they happen to grow up or exist in an environment that is not stressful enough to make them want to drink, or they never touch alcohol in their lives, that gene will remain dormant ("switched off") and they will not become an alcoholic.

But if they choose to drink or something about their environment is stressful enough to trigger alcohol dependency and doesn't help them regulate their consumption, they will quickly fall into a cycle of alcoholism which will become harder to come out of than someone who does not have that wiring ("switched on"). The same can be said for things like mental disorders of schizophrenia or depression. This is why rehabilitation from such issues often involves removing environmental triggers and stressors and training the body to respond in a different way to that which it's naturally disposed to.

As long as the environment remains in such a way that that gene does not get triggered, it will not express, and the person will continue living as though it does not exist. The moment it gets triggered, whether by choice or a significant trauma, it will play out in their lives. The thing about this is that it is often difficult to know what a person is predisposed to from an early age. Family history may give a bit of an indicator, but not always.

This concept becomes quite important when we discuss stimulation in children, because genes and environments can work together here as well, for better or for worse.

Gene-Environment Correlation:

Genetics researchers speak about how a person can have genetics which make them seek out certain environments, for example risky behaviour or really slow and calm environments. Those environments will re-enforce that behaviour whether it is good or not. So, a person who seeks out risky environments will be more likely to engage in riskier behaviour and experience the consequences of that. They may then adopt lifestyles and mentalities that align with that environment. The same for a person in calmer environments. This one, however, can be quite difficult to study as it is not currently possible to draw a direct line between genes, brain function, and behaviour.

Contextual example - Epigenetics and Apartheid

Do you remember the Chronosystem I discussed in Issue 1, Part 4? That plays quite a bit of a role here because when we consider how people think, we need to consider the social climate of the context they have grown up in, not just from a social perspective, but also from an epigenetic one. I am South African, and we have a massive history of oppression and intense dehumanising in this country due to a legacy of Apartheid. This oppression has come with complex trauma which affected and still affects most of our black, coloured, and Indian population. The consequences of this time are very real as there are still some social effects related to it which disproportionately affect certain groups of people.

One thing I try to study in depth is the transmission of trauma across generations (from parent or grandparent to child) and its implications on that child’s development and their future children. What this means is that something like trauma can be inherited and transmitted across generations. So even someone who was not born during Apartheid can be genetically affected by it because their parents were. This can be in physical things, like the resources their parents had access to - some people did not have enough food meaning that their babies grew smaller or stunted. Psychologically, many of us may be carrying defensive measures and do not know whether they came from.

By taking an approach that links the social world and experience (an Apartheid and Post-Apartheid context) with the genetics and biology of development, we can begin to really understand some of the complex effects of such a national trauma and figure out how to heal as well as protect the children of the future from its effects.

The Takeaway
Looking at the role of genes in development, we see that development involves a constant back and forth process between the brain's natural tendency of development and environmental input. These two factors are constantly interacting and influencing each other. In later Issues, I hope to provide more tangible examples of these gene-environment effects in real life, because they have very real effects and are always relevant. For now, we are just focusing on understanding these concepts at the most basic level.

The main takeaway is that as much as we want to predict who a person will become by looking at their biology or genetics, we cannot do that because everything discussed is too complex and interrelated to pull apart at different levels (like how neurons and genes work). We can never fully control the environment or the gene, so it's difficult to make causal conclusions. I.e. we can never say that an outcome is 100% a result of the environment or of biology or of genetics.

However, understanding the contributions of all these things helps us begin to understand development better and implement effective interventions, such as good nutrition, a loving environment, or safety. We always need to look at genetics, biology, and environment together. This is the very essence of Developmental Science.

Share your Comments Below!

Please feel free to reach out with any comments, questions, and child-related stories