David Brooks gets intelligence right -- but genetics wrong

In today's NYTimes, David Brooks has a thoughtful, intelligent column about how mainstream science is gaining a more nuanced understanding of intelligence, and getting past crude measures like IQ. He gets a lot of stuff right. Unfortunately, Brooks gets tripped up near the beginning of his column by the Big Fallacy of "heritability." Brooks writes:

"Intelligence is partly hereditary. A meta-analysis by Bernie Devlin of the University of Pittsburgh found that genes account for about 48 percent of the differences in I.Q. scores."

This is just not correct. It's an entirely understandable mistake on Brooks' part, because so many journalists and even scientists are making it. But what statistical studies like Devlin's miss is that genes actually do not pass any complex traits down on their own. The expression and regulation of genes, biologists now understand, is entirely dependent on their interaction with the environment. You cannot separate one from the other. There is no "nature vs. nurture."

Don't take my word for it. Listen to Michael Meaney, Director of the McGill Centre for the Study of Behaviour, Genes and Environment:

"There are no genetic factors that can be studied independently of the environment, and there are no environmental factors that function independently of the genome. Phenotype emerges only from the interaction of gene and environment. The search for main effects is a fool's errand. In the context of modem molecular biology, it is a quest that is without credibility."

Or take a look at this chart and look at all the influence-arrows going in both directions:

 

The point of the chart is to show how genes are not simple information dispensers, but are dynamic actors in the life of every cell. They don't dictate -- they interact. And how they interact can be affected by just about anything under the sun. Again, Michael Meaney:

"Everything we have learned about molecular biology has shown that gene activity is regulated by the intracellular environment. The intracellular environment is a function of the genetic make-up of the cell and the extracellular environment [which is] also influenced by the environment of the individual."

None of this is yet reflected in how we talk about genetics publicly, thanks in part to this stream of statistical studies that supposedly show what percent of various traits we inherit.

Brooks and the rest of us are victims of the continual and extreme misreading of population studies that seem to show what portion of intelligence comes from genes vs. what portion comes from the environment. When you actually sit down to understand how genetics works, you realize how misleading these studies are. By echoing a strict "nature vs. nurture" sensibility, these heritability estimates are statistical phantoms; they purport to represent something in populations that simply does not exist in actual biology.

If all this has you a little confused, its ok. It should. The ramifications of gene-environment interdependence are so sweeping, it will take a while to come to grips with them. It changes everything we think we understand about "innate," and "hereditary." It opens up a whole new understanding of what human beings are truly capable of. But first we have to describe it correctly. We don't even have right metaphors for genetics to discuss it sensibly in ordinary conversation. That's what I'm spending a good amount of time on now in my book.

Comments

[Romuald]

The expression and regulation of genes, biologists now understand, is entirely dependent on their interaction with the environment. You cannot separate one from the other. There is no "nature vs. nurture."

Are you talking here about any type of gene, or mostly the ones that will get into neurons?
If the former, this goes quite the opposite way what I've learned at school (quite some time ago I admit).
Are blue eyes dependent on how a baby interact with his environment? Could they turn green, or brown, or red based on these interactions?

[LemmusLemmus]

David,

if you found his article thoughtful and intelligent, you might want to read what they had to say about it at Gene Expression:

http://www.gnxp.com/blog/2007/09/progression-of-iq.php

[Pablo]

Please provide some (scientific) evidence that support your claim (links, books, papers).
Then I shall decide whether to agree or disagree with you as I still *believe* in nature over nurture.
My rudimentary knowledge of biology is what dictates that claim, like Romuald said quite simply - Genes don't interact with the environment like how you say they do. They do change according to the environment, but if you're using Darwinian theory to purport that, then you're wrong - mutations aren't interdependent.
I hope you do provide those links or whatever, because, it'd be nice to have my whole view of life destroyed, ;)

[Thel]

Your criticism of Brooks is missing the insight that is provided by the genetic research.

There are constraints on intelligence that are determined by genetic factors. Ceteris paribus, two children with the exact same environmental factors but different genetic predispositions to intelligence (or other traits) will develop different intellectual abilities. An appropriately rich and stimulating environment for various children will cause one to be able to do divide two eight digit numbers in their head at the age of eight (John Von Neumann), while another will become vaguely proficient (say me), and yet another will never even understand multiplication. This is accounted for by genes.

If Mozart were never exposed to music until his twenties he wouldn't have made such accomplishments as a composer. On the other hand, of the hundreds of thousands of children who get comparable musical training from an equally young age, only a tiny handful will make his achievements because they lack the genetic predispositions. There are undoubtedly others with comparable genetic capacities who never achieved because they lacked the rich environment to stimulate optimal development of their brains as well, but that does not eliminate the importance of the role of genes.