Raging against the population genetics machine

By Razib Khan | September 20, 2010 5:32 pm

An interesting readable review in PLoS Genetics taking on population genetics, Frail Hypotheses in Evolutionary Biology:

In conclusion, I return to Michael Lynch’s challenging questions about blind spots and bad wheels in evolutionary biology which motivated this review…Concerning blind spots I have pointed out some limitations of current population genetics. There is too much emphasis on elegant mathematics, and not enough concern for the real values of the critical parameters -in particular, in models of mutation spread and fixation, or in models of optimal mutation rates. Recombination, a crucial genetic mechanism, is misrepresented in the models. Features that looked anecdotal, such as recombination between sister chromatids and germ-line mutations are perhaps central to the mechanisms of evolution in higher organisms. My proposals on mutation strategies…—see also Amos…—lead to rather precise insights on compensatory mutations or polymorphism propagation, yet they are largely ignored by population geneticists.

The beauty of population genetics is that it leads to relatively simple algebras which one can use to guide one’s intuitions. Phenomena such as selection or drift are more than words, they’re specific values. That being said, plenty of readers of this weblog have expressed caution, and skepticism, at the over-utilization of monogenic diallelic models as “quick & dirty” prototypes for evolution more generally. More concretely small changes in parameter values can lead to radically different inferences within the real context of natural history. Excessive reliance on elegant population genetic theory can lead one astray just as excessive reliance on economic theory can. The real world introduces so many complications that discarding too many of them to make a model tractable may render the framework of trivial importance, or even lead one down false paths. I don’t find author’s specific objections of distinction, but the paper is useful as an entry-point into the debate within the literature. The fact that R. A. Fisher, J. B. S. Haldane, and Sewall Wright, did not predict the full path of empirical discovery over the 20th century indicates very concretely the limitations of theoretical frameworks within biology.

CATEGORIZED UNDER: Genetics, Genomics
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  • John Emerson

    Excessive reliance on elegant population genetic theory can lead one astray just as excessive reliance on economic theory can. The real world introduces so many complications that discarding too many of them to make a model tractable may render the framework of trivial importance, or even lead one down false paths.

    In many and perhaps most sciences and social sciences, theorists rank higher than experimentalists, field researchers, and (above all) applied scientists. This is uncomfortably similar to the pre-modern precedence theologians and philosophers had over anyone who worked with their hands — it was only when thinkers started to pay attention to hands-on people (technicians, craftsmen, etc.) that science really took off. Theoretical dominance also favors the insertion of ideology, disfavors attentiveness to historical change and unique particulars (and even to deny the existence of either), and makes it possible for theorists to make their theories impervious to criticism by controlling stipulations, exclusions, default assumptions, etc., of theory.

  • http://blogs.discovermagazine.com/gnxp Razib Khan

    i don’t think theorists are necessarily dominant in biology actually. biology is still dominated by guys who came up through the bench. from what i know theorizing in much of molecular biology is relatively primitive, and there isn’t a large theorist caste. it’s somewhat different in evolution, but even here there are few pure theorists. even fisher and haldane, who were reputedly crappy experimentalists and had no formal biological training, had labs where they tried to do stuff. by analogy, imagine that paul samuelson had been an experimental economist as well as a theorist.

  • Engineer Dad

    Speaking of machines identifying variations in a population’s genes being all the rage, Razib’s old friend and admirer, Robert Plomin, and his research team appear to have identified 200 genes associated with academic performance (IQ) in British school children and has presented his findings to the Royal Society today.

    “The finding emerged from a study of more than 4000 British children to pinpoint the genes and genetic combinations that influence reasoning skills and general intelligence.”

    “One of its main conclusions is that intelligence is controlled by a network of thousands of genes with each making just a small contribution to overall intelligence, rather than the handful of powerful genes that scientists once predicted.”

    Reported in The Australian http://www.theaustralian.com.au/news/nation/found-genes-that-make-kids-smart/story-e6frg6nf-1225926421510

    I suppose Robert Plomin’s findings were inevitable.

  • http://blogs.discovermagazine.com/gnxp Razib Khan

    for readers, never had interactions with robert plomin fwiw. i assume ED is joking.

  • bioIgnoramus

    “One of its main conclusions is that intelligence is controlled by a network of thousands of genes with each making just a small contribution to overall intelligence”: does the word “network” carry some technical meaning there or does it mean “buncha” or “heaps of” or the like?

  • http://downthecellar.blogspot.com Graves

    Razib, you are right that there are relatively few pure theorists in evolutionary biology (and a great deal more who mix theory with empirical work), but the token few who work entirely in theory DO tend to be revered/feared within departments.

    One of the points of the paper that you mention is that theory should be more concerned with the real values of critical parameters. I agree with this on one level, but one of the beautiful things about theory is that it’s much more general than this. If we take Hamilton’s work from the 1960s and focus on using “real” parameter values for relatedness, which of course are going to vary across groups with different life histories and population structure, we miss the more general point. Hamilton’s work lets us think about what the implications are for a changing value of relatedness, without ever having to see a haplodiploid hymenopteran.

  • dave chamberlin

    Robert Plomin was one of 54 signees of an editorial published in the Wall Street Journal attacking the book “The Bell Shaped Curve” in 1994, so I guess Engineer Dad is assuming Razib and Plomin are on opposite sides of the dumb arguments between the “we are all equal” ideologues and the “some races are smarter than others” ideologues. Like a waitress with a bad memory these old emotional opinions just keep coming back.
    I don’t know of any scientists that predicted that a small number of powerful genes contribute to overall intellegence and if they did they didn’t deserve the title scientist.

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  • http://blogs.discovermagazine.com/gnxp Razib Khan

    but the token few who work entirely in theory DO tend to be revered/feared within departments.

    agreed. biologists do view the masters of mathematics with some fear and awe :-)

  • B.B.

    Robert Plomin was one of 54 signees of an editorial published in the Wall Street Journal attacking the book “The Bell Shaped Curve” in 1994

    The editorial had 52 signatories and was defending the basic findings of The Bell Curve. Plomin was one of the signatories.

    Mainstream Science on intelligence (PDF)

  • dave chamberlin

    Well I stand corrected, my apologies to both Engineer Dad and Robert Plomin for a total misrepresentation of their meaning, thanks BB.

  • bioIgnoramus

    “biologists do view the masters of mathematics with some fear and awe”: Christ, some of them fear people who can perform an integration.

  • Azul Mubarak

    Dave Chamberlin: Internet comments and forums are full of such misinformation as your first posting about Plomin and the WSJ editorial. Usually such erroneous comments are not contradicted, because most comment sections are echo chambers for like-minded converts.

    You were lucky this time in being shown to be wrong. Next time, try to be the one who catches the error yourself.

  • miko

    Since Dave is taking such a beating (easy, Azul!) I’ll agree with him that I know of no scientist (and let’s remember, MDs and engineers don’t count) who thought the heritable component of intelligence would be a few genes of large effect.

    On the other hand, I can’t believe anyone still thinks it’s news when someone’s like “we looked at a complex, poorly understood bundle of traits and found that there are many many alleles that show some statistical correlation with their magnitude.” If this was anything but IQ it’d be at the published in the back of PLoS Who Gives A Shit.

    And, yeah, bioIg, “network” is the word media-friendly biologists use when they mean “list.”

    There is an apropos xkcd where you can substitute mathematician for physicist:
    http://xkcd.com/793/

  • Chris T

    Theory is great as long as those using it remember it is a simplification. Problems start arising when practitioners begin to believe the theory holds true regardless of the conditions. It’s helpful to go through the values you’re excluding and assumptions you’re making before applying the theory just to keep in mind that you’re simplifying.

  • dave chamberlin

    I entirerly agree with Azul that I need to double check my comments before stating them here and I take it as a lesson. He wasn’t hard on me,he was factual, this is supposed to be an internet blog with higher standards and I mean to subscribe to them in the future.

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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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