The big idea: is it time to stop talking about “nature versus nurture”? | Books about health, mind and body

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OWhen you hear people conversing in an unfamiliar language, why don’t you even know where one word ends and the next begins? If you are a native English speaker, why is it so difficult to put your mouth around a French or Hebrew “r”, which originates lower in the throat, or the “r” in Spanish or Italian, which is trilled on the tip of the tongue? Your ability to hear and make sounds, and understand their meaning as language, is hardwired into your brain. How you acquire this wiring illuminates an age-old debate about human nature.

During the first few months of your life, your infant brain is bathed in all kinds of information from the world around you, through your senses. This sensory input causes changes in your brain as your neurons fire in various patterns. Certain collections of neurons frequently fire together, strengthening or adjusting their connections and facilitating learning. Others are less used and are pruned, making way for others that are more useful. This process of tuning and pruning is called plasticity, and it happens throughout your life, but a lot in the early years.

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Other people are one of the greatest sources of sensory input to an infant’s brain. As a result, your baby brain has been tuned and honed to detect fine differences in human speech, including a large inventory of consonant and vowel sounds, becoming adept at distinguishing them from each other. But here’s the thing: Babies tend to spend time with caregivers who speak the same language, so you’ve probably missed a lot of sounds only found in other languages. This is one of the reasons why you may have trouble producing or even discerning these unfamiliar sounds today.

This brings us to the age-old debate I mentioned: are your deepest characteristics and abilities present at birth, or are they shaped by your experiences in the world? In other words, is nature or nurture the main driver? We know that part of who you are comes from genes, which contain instructions for building your body and wiring your brain. We also know that the culture you grow up in can shape your brain and your body in fundamental ways.

Few scientists today would say that 100% of your attributes are innate or learned; the debate tends to be about where to draw the line. More recent evidence, however, suggests that the dividing line doesn’t really exist. It turns out that your environment causes certain genes to turn on and off, a process called epigenetics. You also have genes that regulate how much the environment affects you. Genes and environment are so intertwined, like lovers in a fiery tango, that calling them separate names like “nature” and “nurture” is basically pointless.

Take the idea of ​​sleeping on a piece of furniture called a bed, alone or with a partner, in a designated room called a “bedroom,” for a long period of time like eight hours. Such ideas are actually ingrained in your brain through experience and guide your expectations and actions. You can tell because it somehow feels “wrong” to change the habit. If you and your whole family slept every night on straw mats in a room and had to wake up every two hours to tend the fire, it would not seem natural to you, despite the fact that other cultures live on this way.

Even emotions such as joy, sadness and fear, which seem innate and automatic, are actually a product of culture. Suppose you see someone making a wide-eyed, panting face. If you grew up in a Western society you are likely to perceive fear in this face, but if you grew up in Melanesia you are more likely to perceive threat and aggression.

Culture allows one generation to transmit information to the next without it being carried by the genes. Your childhood caregivers organized your physical and social world, and your brain connected to that world. You perpetuate this world and end up passing your culture on to the next generation through your words and actions, wiring their brains in turn. This cultural inheritance is an efficient and flexible partner to genetic inheritance, and means that the process of evolution does not require all of our wiring instructions to be in the genes. The way your brain adapts to the languages ​​you hear as a baby is just one example. Likewise, if you’re exposed to adversity early in life, it can turn on some genes and suppress others, hardwiring your brain to deal with adversity that may arise in the future. Unfortunately, this hardwiring also makes you more susceptible to depression, anxiety, heart disease, and diabetes in adulthood. If you have children, you could pass on some of these characteristics to them through epigenetic changes.

Cultural practices even shape the genetic evolution of our entire species, influencing who is available to breed with whom, and which children are most likely to live to childbearing age. Wealth, class, laws, war, and other human inventions strengthen one group over another, changing the chances that some people will have children together or not at all. Political and religious polarization ensures that people with different beliefs will hardly talk to each other, let alone date or mate. Parents who vaccinate their children against deadly diseases, or choose not to, also make waves in the gene pool. This is how humans, by virtue of the cultures we create, push the evolutionary trajectory of our species.

Culture is therefore not a simple moderator of our biology, but a cause in its own right. I’m not saying your culture determines your destiny, but neither does your genes. Together, your genes and the world you live in make you who you are (for better or for worse). So we are all partly responsible for wiring each other’s brains, and the brains of the next generation, through our words and actions. This is the lesson of the latest science: there is no need to have “cons” in the equation. We just have the kind of nature that needs nurturing, and they’re completely intertwined.

Lisa Feldman Barrett is a professor of psychology at Northeastern UniversityBoston, and the author of Seven and a Half Lessons About the Brain.

Further reading

Not by Genes Alone: ​​How Culture Transformed Human Evolution by Peter J Richerson and Robert Boyd (Chicago, £27)

Sense and Nonsense: Evolutionary Perspectives on Human Behavior by Gillian R Brown and Kevin N Laland (Oxford, £34.49)

The Triple Helix by Richard Lewontin (Harvard, £24.95)

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