How Did I Become This Way?

When you hear people speaking in a language you don’t know, why can’t you tell where one word ends and the next begins? If you’re a native English speaker, why is it so hard to pronounce the French or Hebrew guttural “r,” or the Spanish or Italian “r” that’s rolled with the tip of the tongue? The ability to hear and produce sounds, and to mentally “translate” them into language, is biologically programmed into our brains. How this biological potential develops in a person sheds light on the age-old debate about human nature.

In the first few months of life, a baby’s brain is flooded with all kinds of information from the surrounding world, coming in through the senses. Incoming sensory data trigger changes in the brain, activating neurons in various configurations that are reinforced by forming synaptic connections. Some groups of neurons are often activated together, strengthening or fine-tuning their synaptic links, which helps with learning. Other neural networks are used less and gradually eliminated, making room for more useful connections. This process of synaptic tuning and pruning is called neuroplasticity, and it happens throughout your life, but is especially intense in the first few years after birth.

The Role of Language and Culture in Brain Development

One of the biggest sources of sensory data for a baby’s brain is other people. For this reason, the infant brain has evolved to detect subtle differences in human speech, including the ability to distinguish a wide range of consonant and vowel sounds, which eventually leads to the ability to tell one language from another. However, children usually spend almost all their time with adults who speak the same language, so many sounds that exist only in other languages never enter their awareness. This is one reason why it may be so hard for you today to reproduce or even distinguish unfamiliar sounds.

Nature vs. Nurture: A False Dichotomy

This brings us back to the long-standing debate I mentioned earlier: are our personal traits and abilities set at birth, or are they shaped by our experiences in the world? In other words, what is the main driving force: genetics or upbringing? We know that part of our personal “story” is written in our genes, which contain instructions for building our bodies and brains. We also know that the culture we grow up in can fundamentally affect both our brains and bodies.

Few scientists today would claim that 100% of your qualities are either innate or acquired. The debate now is usually about where the dividing line lies. However, new scientific evidence suggests that such a line doesn’t really exist. It turns out that the environment prompts certain genes to turn on and off—a process called epigenetics. We also have genes that regulate how much the environment can influence us. Genes and environment, like partners in a passionate dance, are so closely intertwined that it makes no sense to try to balance their influence based on a false opposition.

How Experience Shapes Expectations and Behavior

Suppose you sleep on a piece of furniture called a “bed,” alone or with a partner, in a special room called a “bedroom,” for a long period, say eight hours. These ideas are “installed” in our brains through experience and then guide our expectations and actions. You can see the power of these familiar concepts in how sleeping differently feels “wrong.” If you and your whole family slept every night on straw mats in one room, waking up every two hours to keep a fire going, then eight hours of sleep in a separate bedroom would feel unnatural to you, even though that’s the norm in other cultures.

Emotions and Cultural Interpretation

Even basic emotions like joy, sadness, and fear, which seem innate and automatic, are actually products of culture. Suppose you see someone’s eyes suddenly widen and their mouth open. If you grew up in Western culture, you’ll likely interpret this as an expression of fear. But if you grew up in the Melanesian islands, you’re more likely to see this facial expression as a sign of threat or aggression.

Cultural Inheritance and Evolution

Culture allows for the transmission of information across generations without the need for genetic carriers. The important figures of your childhood shaped your physical and social world, and your brain “plugged into” this pre-existing world. You extend the existence of this world and eventually pass on culture to the next generation through language and actions, “connecting” the brains of those who come after you. This mechanism of cultural inheritance works hand in hand with genetic inheritance, which means that evolution is not limited to instructions encoded in genes alone. How your brain tunes itself to the languages you hear in childhood is just one example. Similarly, if you faced hardship and deprivation in your youth, that experience could activate the expression of some genes and suppress others, preparing your brain to cope with future adversity. Unfortunately, this presetting also makes you more vulnerable to depression, anxiety, heart disease, and diabetes in adulthood. If you have children, you may pass on some of these traits through epigenetic changes.

How Culture Directs Human Evolution

Cultural practices guide the genetic evolution of our species by influencing who can have children with whom and which children are more likely to survive to reproductive age. Wealth, class, laws, wars, and other human inventions allow one group to dominate another, changing the odds of certain people having children together—or at all. Political and religious polarization means that people with different beliefs are unlikely to even talk to each other, let alone form romantic relationships or have children. Parents who vaccinate their children against deadly diseases, or choose not to, also change the gene pool. It is human-created culture that sets the evolutionary trajectory of our species.

The Interdependence of Genes and Culture

So, culture is not just a moderator of our biology, but a full-fledged causal factor. I’m not saying that culture determines your destiny, but neither do your genes. The interaction of genetics and the world you live in makes you who you are—for better or worse. In this way, we all share some responsibility for “connecting” each other’s brains and the brains of the next generation through language and actions. This is the lesson of modern science: when it comes to the origins of humanity, there should be no “versus,” as in the opposition of genetics and upbringing. More accurately, we are carriers of genetics that require nurturing, and only their interaction makes us human.