Applying intelligence to genes for intelligence

Carl Zimmer has an excellent write up on the new new Nature study of the variants associated with IQ, In ‘Enormous Success,’ Scientists Tie 52 Genes to Human Intelligence.

The issue with intelligence is that it’s a highly polygenic trait for which measurement is not always trivial. You need really large sample sizes. It’s about ten times less tractable than height as a quantitative trait. There are still many arguments about its genetic nature (though a majority position that it’s not rare variants of large effect seems to be emerging).

But all in good time.

Science is divided into many different fiefdoms, and people don’t always talk to each other. For example I know a fair number of population genomicists, and I know behavior geneticists who utilize quantitative genomic methods. The two are distinct and disparate groups. But the logic of cheap sequencing and big data is impacting both fields.

Unfortunately when you talk to population genomicists many are not familiar much with psychology, let alone psychometrics. When it comes to the behavior geneticists many come out of psychology backgrounds, so they are not conversant in aspects of genetic theory which harbor no utility for their tasks at hand. This leads to all sorts of problems, especially when journalists go to get comments from researchers who are really opining out of domain.

Some writers, such as Carl Zimmer, are very punctilious about the details. Getting things right. But we have to be cautious, because many journalists prefer a truth-themed story to the truth retold in a story format. And, some journalists are basically propagandists.

Over the next five years you will see many “gene and IQ” studies come out, with progressively greater and greater power. Read the write-ups in The New York TimesScience, and Nature. But to my many readers with technical skills this is what you should really do:

  1. pull down the data.
  2. re-analyze it.

My plain words are this: do not trust, and always verify.

I’m a big fan of people educating themselves on topics which they have opinions on (see: population genetics). If intelligence is of some interest to you, you should read some things. Arthur Jensen’s classic The g Factor: The Science of Mental Ability can be quite spendy (though used copies less so). But Stuart Ritchie’s Intelligence: All That Matters and Richard Haier’s The Neuroscience of Intelligence are both good, and cheaper and shorter. They hit all the basics which educated people should know if they want to talk about the topic of intelligence in an analytical way.

4 thoughts on “Applying intelligence to genes for intelligence

  1. “If you try to predict height using the genes we’ve identified in Europeans in Africans, you’d predict all Africans are five inches shorter than Europeans, which isn’t true,” Dr. Posthuma said.

    Didn’t you post a graph from a paper about exactly this? I can’t find that post and/or paper now.

    Is this true? What does it mean?

    Of course if you study Europeans to find genes for height then your predictions of the heights of Africans will be compressed.
    But what will the center be? I would have expected it to be the European mean. I guess the deviation must mean that there is has been recent selection on Europeans for height. Is the predicted African height a reasonable guess for the height of the most recent common ancestor?

  2. “I guess the deviation must mean that there is has been recent selection on Europeans for height.”

    It all depends on how you define “recent.” The average height of Europeans roughly 800 or 1000 years ago during the prosperous Medieval Warm Period/High Middle Ages when food was abundant was almost as tall as today. I daresay that the addition of a few modern vitamins/micronutrients that one finds in todays food would have given them the extra half inch to make them just as tall as the contemporary populace. This implies that selection for height occurred prior to that era.

  3. “It’s about ten times less tractable than height as a quantitative trait.”

    Is that accurate? Isn’t >300 hits with ~80k genomes actually quite good? I looked back at some height studies, and it seems IQ might even be more tractable than height (putting aside the massive problem of obtaining combined genome/IQ data).

    I know years of education requires much larger sample sizes, but that’s only a rough proxy for IQ and most of the variance is non-genetic.

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