There Is No Nature/Nurture Distinction | Nature/Nurture | Children Intelligence

New science shows genes and environment are deeply intertwined.

by David Shenk

March 10, 2010


An excerpt from The Genius in All of Us


To say that there is much we don’t control in our lives is a dramatic understatement, roughly on the order of saying that the universe is a somewhat large place. To begin with, there are many influences we can’t even detect. In 1999, Oregon neuroscientist John C. Crabbe led a study on how mice reacted to alcohol and cocaine. Crabbe was already an expert on the subject and had run many similar studies, but this one had a special twist: he conducted the exact same study at the same time in three different locations (Portland, Oregon; Albany, New York; and Edmonton, Alberta) in order to gauge the reliability of the results. The researchers went to “extraordinary lengths” to standardize equipment, methods, and lab environment: identical genetic mouse strains, identical food, identical bedding, identical cages, identical light schedule, etc. They did virtually everything they could think of to make the environments of the mice the same in all three labs.

Somehow invisible influences intervened. With the scientists controlling for nearly everything they could control, mice with the exact same genes behaved differently depending on where they lived. And even more surprising: the differences were not consistent, but zigged and zagged across different genetic strains and different locations.

This was unforeseen, and it turned heads. Modern science is built on standardization; new experiments change one tiny variable from a previous study or a control group, and any changes in outcome point crisply to cause and effect. The notion of hidden, undetectable differences throws all of that into disarray. How many assumptions of environmental sameness have been built right into conclusions over the decades? What if there really is no such thing?

What if the environment turns out to be less like a snowball that one can examine all around and more like the tip of an iceberg with lurking unknowables? How does that alter the way we think about biological causes and effects?

Something else stood out in Crabbe’s three-city experiment: gene-environment interplay. It wasn’t just that hidden environmental differences had significantly affected the results. It was also clear that these hidden environments had affected different mouse strains in different ways – clear evidence of genes interacting dynamically with environmental forces.

But the biggest lesson of all was how much complexity emerged from such a simple model. These were genetically pure mice in standard lab cages. Only a handful of known variables existed between groups. Imagine the implications for vastly more complex animals – animals with highly developed reasoning capability, complex syntax, elaborate tools, living in vastly intricate and starkly distinct cultures and jumbled genetically into billions of unique identities. You’d have a world where, from the very first hours of life, young ones experienced so many hidden and unpredictable influences from genes, environment, and culture that there’d be simply no telling what they would turn out like.

Such is our world. Each human child is his/her own unique genetic entity conceived in his/her own distinctive environment, immediately spinning out his/her own unique interactions and behaviors. Who among these children born today will become great pianists, novelists, botanists, or marathoners? Who will live a life of utter mediocrity? Who will struggle to get by? We do not know. 4 ways toward excellence4 ways to guide your child towards excellence – read the excerpt here.

What we do know is that our brains and bodies are primed for plasticity; they were built for challenge and adaptation. This is true from life’s earliest moments. According to neuroscientists Mark H. Johnson and Annette Karmiloff-Smith, “Recent reviews of pre- and postnatal brain development have come to the conclusion that brain development is not merely a process of the unfolding of a genetic plan.”

Intelligence is not fixed but waiting to be developed. Athletic prowess is not preordained but awaits training. Musical ability lies dormant in all of us, calling for early and sustained incantation. The potential for creativity is built into the architecture of our brains. All of these are a function of influence and process – far from fully controllable, but also quite the opposite of fixed and predetermined.

The parent’s job, then, is to respect and engage in that process. Rather than waiting for natural gifts to sprout, we must immediately dive into the process, embracing the inseparability of nature and nurture. We know that genes are playing a key role and that their expression is being determined every moment by the quality of the life our child leads. We know that we are helping to choose our child’s own jukebox tune. Our job is to find the process that produces the best possible individual.

Ultimately, of course, the life goal will be up to the individual. But parents can sow certain seeds and water them. The nature/nurture distinction is a false one.

From The Genius in All of Us by David Shenk Copyright © 2010 by David Shenk. Excerpted by permission of Doubleday, a division of Random House, Inc. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.

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