How much of life is predetermined by one’s environment and genetics?

Allison Hu
Mar 2, 2024
4 min read

Written by Meiqi Tan

October 2023

What exactly makes you…you? Are your ideas and beliefs simply a collection of everything you’ve experienced, or a fundamental, intrinsic part of you? Well first, let’s try to find a way out of this existential crisis—starting with a deep dive into some science.

// Image from Getty/Wired.

Nature vs. Nurture

The nature-nurture debate stems from questions of whether an organism’s development is more influenced by their environment or the genetic information embedded in DNA [1]. Nature refers to the way our surroundings impact our current and future states—who we are now, and who we might become in the future. Genetics refers to hereditary traits, otherwise known as inherited traits, from a previous generation.

What do we know?

Following the scientific method, the first step involves observing our surroundings. Often, siblings typically look similar to one another if they share the same birth parents. While trends and patterns can be spotted for similarities, evidently not all siblings are identical or express uniform personalities with one another or with parents—this is, of course, in consideration that human cloning does not exist as of 2023.

Human behavior, unlike physical traits such as eye color or blood type, derives from a more complex process and is not wholly decided by genetic inheritance. For instance, some personalities or acquired traits—or traits developed from life experiences—cannot be directly transferred to an offspring. In other words, parents can’t simply osmose their entire wealth of knowledge and experiences to their children biologically. What parents do pass down, however, are genes which code for proteins; ironically, proteins then deactivate or activate certain genes to halt the production of other proteins. This process creates specialized cells that influence characteristics ranging from one’s outward behaviors and appearances to billions of reactions at the cellular level [3].

In a research conducted on media use and mental health, scientists found patterns associating the time and effects of media usage with genetics [7]. Since technology has become nearly ubiquitous in the twentieth century, the study hoped to measure positive and negative implications of using social media [7]. The results, along with various research in the past, suggested that genetics can determine unique differences in our taste and desire for certain activities [7][8].

Epigenetics

With a simple understanding of genetics, let’s backtrack to the correlation between environment and behavior. In the field of epigenetics1, which studies the effect of behavior and environment on genetic expression2[5], researchers have investigated and theorized that early exposure to specific environments can increase a predisposition to certain tendencies and health conditions [4]. However, little is known about the exact science behind this process. One theory suggests that experiences can modify an individual’s stress responses if genes can’t respond normally due to chemical changes [4].

In a study conducted on rats, a model organism whose studies can help with predicting human or mammalian reactions, researchers discovered certain traits in a parent led to a preponderance of progeny adopting the same traits [4]. Initially, this result suggests a correlation between the trait and the gene passed down; however, when the offspring of a parent without the trait was raised by another parent with the trait, the offspring developed that very trait [4]. The results indicate that a mix of both environmental and genetic factors can influence behaviors.

Notably, in epigenetic inheritance, specific epigenetic tags are also passed down to offsprings. Essentially, these tags are a long-term record of experiences in cells, which adapt and stabilize based on changes in an environment [10]. For the entire life cycle, signals are incessantly transmitted and influence the epigenome [10]. When a pregnant mother suffers from malnutrition or stress hormones, they may develop epigenetic tags in response and transfer them to the fetus [10]. The tags can play a role in behavior, including increased suicidal tendencies and irregular or uncommon responses to stress [10]. In this sense, parents do pass their experiences down, through the cellular level. It is important to note, however, that only 1% of epigenetic tags get passed down, so an offspring likely won’t contain the exact same tags from generations prior.

“Epi-” means “on” or “above” in Greek, so epigenetics is related to studying factors outside of genetics [6].
Epigenetic influences do not alter a cell’s genetic code [5], but simply how the code is read and expressed—same blueprint, slightly different buildings.

So what?

So far, the original question has yet to be fully answered. Are we who we are because of our environment or because it’s predetermined by genes passed down through the centuries?

With a solid understanding of several determinants of behavior, we can now piece together a clearer picture. As humans, a great deal of our behavior is set by societal standards and peer expectations, but a considerable amount of behavior is attributed to genetics and parent experiences—things completely out of our control—but also personal values gathered from an individual’s unique experiences. Scientifically, experiences serve to develop instinctive responses to stressful situations with a higher chance of survival [9]. Uniqueness serves to benefit us. It’d be difficult to quantify the exact impact of so much outside of our control, but it might help to understand and shape what we do have control of.

So, really, your personality is uniquely defined by your own parameters, and while the role of genes and environment can influence how you perceive the world, they can’t define your entire life. Ultimately, a considerable amount of life is predetermined, but as Theodore Roosevelt once stated, “Do what you can, with what you have, where you are.” It might just be human nature to go against nature, and believing in change is often the first step to bringing about change. ❧