How Genes Really Work

By David Shenk
Autorecessive.jpg

In my first post, I listed three separate chunks of science that, when seen together, suggest a radical new understanding of talent and intelligence. Today, I will focus on the first piece, genetics. I'll begin by asking for a crazy indulgence:

Forget everything you think you know about genes and heredity.

You've heard about Gregor Mendel and his pea plant experiments; about dominant and recessive traits (brown eyes/blue eyes); about genes being "blueprints"; about the breast cancer gene and the depression gene; about twin studies. You've been told over and over again that the genes we inherit from our parents contain detailed instructions on whether we will be tall or short, fast or slow, skinny or fat, smart or dim-witted, musical or tin-eared.

But it's not true.

Ok, many bits of it are true. But the big picture -- the notion that our genes contain information on what each of us will be like -- is very badly distorted. Scientists know this already; they just haven't successfully communicated it to the rest of us. We've entered this very strange zone: as geneticists hurtle themselves into extraordinary 21st century discoveries and opportunities, the general public is stuck in a 19th century understanding of genetics. I suggest that this is a very dangerous disconnect, and is something teachers and journalists must do something about.

Genes matter, a lot. Let me make that clear as I can. Genes powerfully influence absolutely everything we are and everything we do. We're all genetically distinct from one another, and those differences guarantee that we will each have a unique look and unique abilities.

But what those differences specifically turn out to be is not pre-ordained. We've been led to believe that many of our features are innate. But the very notion of innate is flawed, because from the first moment of your conception to your very last breath your genes are in a dynamic improvisation with the world around you.

To show you that I'm not making this stuff up, here is how geneticists Eva Jablonka and Marion Lamb put it:

"The popular conception of the gene as a simple causal agent is not valid. The gene cannot be seen as an autonomous unit -- as a particular stretch of DNA which always produces the same effect. Whether or not a length of DNA produces anything, what it produces, and where and when it produces it may depend on other DNA sequences and on the environment."

Rather than being detailed blueprints, instructions, genes are more like knobs and switches that constantly get turned on and off by other genes and by environmental signals. (The turning on and off is called "genetic expression.")

That's why you hear so much these days about genes being "probabilistic." What that clunky word means is that it's fairly rare for certain genes to be 100% associated with certain outcomes. More commonly, certain genes interact with other common environmental and lifestyle variables to produce an outcome.

The breast cancer gene mutation, for example, doesn't cause breast cancer. Rather, a particular genetic variant interacts with many external influences to produce cancer more often than in people with different variants of the gene.

This same dynamic also means that your DNA cannot make you inherently smart or talented. It guarantees your uniqueness, for sure, but what that uniqueness will actually turn out to be is up to an infinitely complex set of gene-environment interactions influenced by nutrition, environment, culture, human whim, and many unknowns.

Another way to put it is this: we've spent a century trying to figure out how to separate nature from nurture, when in fact, they are biologically inseparable.

There's much more to say, but that's a big-picture overview.

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Further Reading:

This article available online at:

http://www.theatlantic.com/national/archive/2009/07/how-genes-really-work/22007/