Nature vs. Nurture

Nature vs. Nurture: How Biology Shapes Who We Become

By: Rohan Sachdeva

You’ve probably heard the question before: Are we shaped more by our genes, or by the environments we grow up in? The classic debate between nature and nurture. Either your DNA decides who you are, or your life experiences do. Biology, however, tells a more complicated story.

At birth, genes appear to hold the upper hand. You inherit a complete set of DNA from your parents, containing instructions that influence traits like height, metabolism, and disease risk. It is easy to assume that once those genes are set, the outcome is fixed.

But the story starts changing almost immediately.

Even before you are born, your environment begins shaping how those genes are used. Nutrient availability, maternal stress, and oxygen availability all influence how cells divide and specialize. Identical twins, who share the same DNA, may already show differences in gene activity before birth. The genetic code is the same, but how it is read is not.

This is where epigenetics comes in.

Epigenetics refers to the chemical tags that attach to DNA or the proteins surrounding it. These tags do not change the genetic code itself but rather control whether certain genes are turned on or off. Your genome contains thousands of possibilities, but epigenetic marks decide which ones are actually used.

What makes this even more intriguing is that some of these tags can be shaped by the environment over time. Stress, nutrition, and exposure to toxins can alter epigenetic marks on genes involved in metabolism, brain development, and stress regulation. These epigenetic changes can be passed on to future generations.

After birth, environmental influence continues, particularly during early development. The brain forms far more neural connections than it will ultimately keep. Our experiences determine which neurons are reinforced and which are pruned away.

Language is a clear example. Humans are genetically prepared to learn language, but which language and how fluently depends entirely on exposure. Without the right experiences during early developmental windows, even a healthy brain may struggle later on. Stress works similarly. Genes influence how sensitive your stress system is, but early experiences help set its baseline. Chronic stress during development can modify gene expression in pathways that regulate cortisol release, leading to a more reactive stress response throughout life. The same genes, placed in different environments, can lead to very different outcomes.

At this point, it may seem like nurture is doing most of the work.

But genes still matter. Not everyone responds to the same environment in the same way. Some people are more resilient to stress, while others are more vulnerable. Genetic differences in neurotransmitters, hormone receptors, and immune signalling help explain these variations. 

But wait, there’s more. The enzymes that add and remove epigenetic tags are encoded by genes themselves. Because of this, your DNA influences how flexible your gene expression can be in response to experience. In a sense, the degree to which your environment can shape your personality is partly inherited.

And so, the answer becomes clear. Nature and nurture are not rivals; they are partners. Genes provide the framework, and the environment fine-tunes the result. Development is a constant feedback loop between biology and experience. Your genes shape how you respond to the world, and the world shapes how your genes are expressed. Who you become is written by both, together.