The Genetics of Stoopid

Ask not what your genes have done to make you smart, but what they’ve done to make you stupid.

That’s the gist of an idea offered recently by neurogeneticist Kevin Mitchell in a “The genetics of stupidity,” a fun, provocative post at his blog, Wiring the Brain. Today  I unpack this idea a bit in a piece in a column at the New York Times, titled “Smart is the Norm, Stupidity Gets More Interesting?” It’s first of a series I’ll be doing for the Times’ Mind column, part of the Science section. Here’s the opener of today’s post:

Few of us are as smart as we’d like to be. You’re sharper than Jim (maybe) but dull next to Jane. Human intelligence varies. And this matters, because smarter people generally earn more money, enjoy better health, raise smarter children, feel happier, and, just to rub it in, live longer as well.

But where does intelligence come from? How is it built? Researchers have tried hard to find the answer in our genes. With the rise of inexpensive genome sequencing, they’ve  analyzed the genomes of thousands of people, looking for gene variants that clearly affect intelligence, and have found a grand total of two.

One determines the risk of Alzheimer’s and affects I.Q. only late in life; the other seems to build a bigger brain, but on average it raises I.Q. by all of 1.29 points.

Other genetic factors may be at work: A report last year concluded that several hundred gene variants taken together seemed to account for 40 to 50 percent of the differences in intelligence among the 3,500 subjects in the study. But the authors couldn’t tell which of these genes created any significant effect. And when they tried to use the genes to predict differences in intelligence, they could account for only 1 percent of  the differences in IQ.

“If it’s this hard to find an effect of just 1 percent,” Robert Plomin, a professor of behavioral genetics at King’s College London, told New Scientist, “what you’re really showing is that the cup is 99 percent empty.”

But is the genetic cup really empty, or are we just looking for the wrong stuff? Kevin Mitchell,  a developmental neurogeneticist at Trinity College Dublin, thinks the latter. In an essay he published in July on his blog,  Wiring the Brain, Dr. Mitchell proposed that instead of thinking about the genetics of intelligence, we should be trying to parse “the genetics of stupidity,” as his title put it. We should look not for genetic dynamics that build intelligence but for those that erode it.

From there the column looks at three of those erosive dynamics: mututional load, developmental stability, and that odd duck of development, asymmetrical symmetry. Please do get on over and check out the whole thing.  When you’re done, take a look at Mitchell’s’ original Genetics of Stupidity post, his related posts on  “wild-type” humans (including Brad Pitt), Why have genetic linkage studies of schizophrenia failed?, Are human brains especially fragile?, and It’s not the crime, it’s the cover-up: reactivity in the developing brain and the emergence of schizophrenia. This is a genetics of decrement, essentially, which means, above all, that ain’t none of us perfect. Lots of provocative ideas, and a nice look at how one scientist is using a blog to explore implications of the research he’s doing and reading.

If your own randomly developed neurodevelopmental pathways lead you to favor videos over words, you might prefer Mitchell’s recent 5-minute Ignite talk, where he covers many of these ideas in fast motion:

3 responses

  1. Thank you, David for putting more light on the subject of intelligence (or lack thereof) and the neurogenetics now yielding from the study of it. And also bringing to our attention a fascinating Video presentation.

    Essentially, what Dr. Mitchell concludes in his video talk is that “luck” is a genetically conferred trait. That is to say, the influence of chance itself is modulated by a particular gene’s presence. What he doesn’t state is that whether or not that gene expresses itself is not the result of chance, but the result of whether environmental interaction allows that same gene to be expressed. Therefore, even if you have the genetics for “greater chance”, this doesn’t mean you will actually get to enjoy that gene’s influences unless environment, by chance, causes it to be expressed [epigenetics]. So it it fair to conclude that stupidity is simply a matter of luck, good or bad?

  2. The whole genetics-of-intelligence thing strikes me as a perfect case of looking for one’s keys under the spotlight. Not that there aren’t heritable contributions to intelligence, and rare variants & other non-common-SNP types of variation will reveal more than we’ve identified thus far, but environment is going to be so much more powerful (and tractable). But so much less amenable to studying in a genetics lab.

  3. Hi David, this is an interesting idea, but I see a potential flaw in the reasoning. From what I gathered in the New York Times science podcast, you seem to suggest that the brain is designed for a particular environment. Therefore, a certain percentage of the mutations in the next generation would be detrimental simply by pure statistics. However, this assumes that the optimum environment stays constant from one generation to the next. But given the fantastic rate of change in our modern culture, we can’t say that the future generation is necessarily suboptimal. One can just as well envision a static brain that falls out of favor with the environment due to obsolescence, as the environment changes.

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