Heritability and genes as causes

By Razib Khan | December 22, 2010 11:25 am

Since the beginning of this weblog (I’ve been writing for eight years) heritability has been a major confusion. Even long time readers misunderstand what I’m trying to get at when I talk about heritability. That’s why posts such as Mr. Luke Jostins‘ are so helpful. I had seen references to a piece online, The Causes of Common Diseases are Not Genetic Concludes a New Analysis, but I hadn’t given it much thought. Until Ms. Mary Carmichael’s post DNA, Denial, and the Rise of “Environmental Determinism”. She begins:

Michael Pollan, the well-known writer on food and agriculture, is a smart guy. His arguments tend to be nuanced and grounded in common sense. I like his basic maxim on nutrition – “Eat food. Not too much. Mostly plants” – so much that I recently promoted it in a Newsweek cover story. He’s the last person I’d suspect of reactionary thinking, which is why I wish I didn’t have to say this: Michael Pollan has made a deeply unfortunate mistake.

A few days ago, speaking to his 43,000 followers on Twitter, Pollan linked to an essay written by an environmental advocacy group that spends much of its time fighting the depradations of Big Agriculture. Curiously, the essay wasn’t about ecological destruction or even about agriculture. It was about human genetics. It argued that since genetics currently can’t explain everything about inheritance, genes must not influence the development of disease, and thus the causes of illness must be overwhelmingly environmental (meaning “uninherited” as opposed to “caused by pollution,” though the latter category of factors is part of the former one). This was a little like arguing that your engine doesn’t power your car because sometimes it breaks down in a way that confuses your mechanic — and concluding that gasoline alone is sufficient to make a car with no engine run. But Pollan took the argument at face value. He said it showed “how the gene-disease paradigm appears to be collapsing.” He was troubled that its contentions apparently had gone unnoticed: “Why aren’t we hearing about this?!”

Of course I had seen Dr. Daniel MacArthur’s post Bioscience Resource Project critique of modern genomics: a missed opportunity in my RSS, but when I started reading the rebuttal I immediately thought “Dr. Dan’s interlocutors sound kind of dumb,” and I stopped reading. After reading the post I don’t think they’re dumb, I think they’re being lawyerly. Much of the piece is a rhetorical tour de force in leveraging the prejudices and biases of the intended readership. This is the Intelligent Design version of Left-wing “Blank Slate” Creationism.* They smoothly manipulate real findings in a deceptive shell game intended to convince the public, and shape public policy. Their success is evident in Pollan’s response. “X paradigm appears to be collapsing.” “Why aren’t we hearing about this?” Does this sound familiar? Like Dr. MacArthur I think some of the criticisms within the piece are valid. Despite not being hostile to the maxim “better living through chemistry,” I do think that there has been an excessive trend toward pharmaceutical or surgical “cures” in relation to diseases of lifestyle (anti-depressants, gastric bypass, etc.). But we go down a very dangerous path when we make recourse to shoddy means toward ostensibly admirable ends. This sort of discourse is not sustainable! (just used a buzzword intended to appeal right there!)

I honestly can’t be bothered to say much more when so many others already have. This is a boat I missed. But if some of what I say above isn’t clear, I recommend you read the original essay. Then read Dr. MacArthur and Ms. Carmichael. If you’re hungry for more, Ms. Carmichael has a helpful list of links.

* Left Creationism had its most negative manifestation as Lysenkoism, but it suffuses the outlook of many who fear the emergence of a new Nazi abomination. Leon Kamin in the 1970s even claimed that IQ was not heritable at all! Though he backed off such an extreme position, it shows how confident he was that could claim such a thing.

CATEGORIZED UNDER: Genetics, Genomics
  • miko

    That is a shame…I really enjoyed The Botany of Desire, it was a nice angle on plant domestication grounded in some competency with genetics and evolution.

    That article is a travesty of distortion…(and onur: note the excellent credentials of the authors). I doubt the authors are ignorant of the complexities they are exploiting to appeal to a particular audience or agenda. There are kernels of valid criticism about how the biotech industry in particular has approached the concept of “disease genes.” (For a much better one, see Adam Wilkins in Bioessays several years ago.)

    But this public conversation can never move forward if we constantly have to go back to just getting our terms straight: explaining things like heritability, pleiotropy, gene x environment interaction… even science journalists for the most part seem not to have a basic conceptual framework for talking about or understanding results in quantitative genetics. I guess this kind of crap is the other side of the “scientists discover gene for X” coin.

  • http://blog.openhelix.com Mary (not Carmichael)

    I knew some people thought I had over-reacted to the initial item/press release. And I might have just let it die until Pollan tweeted it so far and wide. Then I knew it required larger damage control.

    I’m delighted to have you human genetics folks on board now. But those of us who have been dealing with these folks on plant science issues for a long time know what they are up to. Some of them are even trying to block funding for research training in developing countries because the bill contains the word “biotech”. It doesn’t matter if you try to explain to them that scientists in Africa need training for managing seed banks, or doing MAS. They use “biotech” as a club to stop research and training. Here’s the bill’s author trying to straighten them out, to no avail: http://thehill.com/opinion/letters/95017-rep-lugar-no-mandate-for-genetic-modification

    They are seriously anti-science. This was just a particularly unusual attack, and I’m glad it caught the eye of the genetics community. They are using the same strategies as anti-vaxxers and creationists. They techniques are getting more refined, I have to say. I’m calling it “crank evolution”. It’s in linkage with “crank magnetism”.

  • bioIgnoramus

    “Leon Kamin in the 1970s even claimed that IQ was not heritable at all!” He wasn’t alone. Back in the 60s when I read the popular psychology paperbacks of Eysenck, I learnt that the “inheritance” proponents were the guys who argued that both inheritance and environment mattered – their opponents asserted that only environment mattered. This preposterous gibberish seems still to infest the schoolteacher population.

  • Chris T

    Leon Kamin in the 1970s even claimed that IQ was not heritable at all!

    I still see people who ostensibly accept evolution claim that intelligence isn’t heritable, never mind that such a position would make human evolution by natural means logically impossible. We apparently do not exist.

  • Ethan

    “such a position would make human evolution by natural means logically impossible.”

    I think it would just make evolution in intelligence impossible. Which could be rhetorically reconciled with evolution either with a Behe-like assumption that all observed forms of human intelligence were present in potentia in the first anatomically modern human, or by claiming that intelligence is not a thing so its non-evolution is trivial.

    This is quibbling since I agree with your probable enthymeme, that the evolution of human intelligence is inextricable from any true account of human evolution. I’d be delighted to hear that someone had tried the Behe-like method though.

  • http://bluetenlese.wordpress.com M. Möhling

    Luke Jostins: “… you should definitely not be using heritability within populations to try and infer genetic differences between populations …”
    Do you agree? This admonition seems not to refer exclusively to twin studies.

  • Pingback: Friday Fluff – December 24th, 2010 | Gene Expression | Discover Magazine

  • Chuck

    Moehling said: Luke Jostins: “… you should definitely not be using heritability within populations to try and infer genetic differences between populations …”
    Do you agree? This admonition seems not to refer exclusively to twin studies.

    Disagree. If Jostin said “you definitely [can't] infer between group heritability from within group heritability” he would be correct. But he didn’t say that. He said that you can’t use within group heritability to infer between group heritability — which is silly.

    Imagine a trait W that is 100% heritable within both population A and B. If one can rule out all environmental factors (X) that might uniquely affect A or B, one could infer a genetic component to the difference between A and B. If the heritability was <100% within A and B, one could make a similar inference, if one had some additional information.

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This blog is about evolution, genetics, genomics and their interstices. Please beware that comments are aggressively moderated. Uncivil or churlish comments will likely get you banned immediately, so make any contribution count!

About Razib Khan

I have degrees in biology and biochemistry, a passion for genetics, history, and philosophy, and shrimp is my favorite food. In relation to nationality I'm a American Northwesterner, in politics I'm a reactionary, and as for religion I have none (I'm an atheist). If you want to know more, see the links at http://www.razib.com

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