NYT: "In ‘Enormous Success,’ Scientists Tie 52 Genes to Human Intelligence"
May 22, 2017, 02:30 PM
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From the New York Times:
In ‘Enormous Success,’ Scientists Tie 52 Genes to Human Intelligence

Carl Zimmer

MATTER MAY 22, 2017

In a significant advance in the study of mental ability, a team of European and American scientists announced on Monday that they had identified 52 genes linked to intelligence in nearly 80,000 people.

These genes do not determine intelligence, however. Their combined influence is minuscule, the researchers said, suggesting that thousands more are likely to be involved and still await discovery. Just as important, intelligence is profoundly shaped by the environment.

Still, the findings could make it possible to begin new experiments into the biological basis of reasoning and problem-solving, experts said. They could even help researchers determine which interventions would be most effective for children struggling to learn.

“This represents an enormous success,” said Paige Harden, a psychologist at the University of Texas, who was not involved in the study.

Paige Harden was a co-author of the Vox “Junk Science” article last week about how Charles Murray is 80% right and his critics 80% wrong, but the know-nothings are still on the side of the angels.
For over a century, psychologists have studied intelligence by asking people questions.
In other words, IQ tests.
Their exams have evolved into batteries of tests, each probing a different mental ability, such as verbal reasoning or memorization. …

Each test-taker may get varying scores for different abilities. But over all, these scores tend to hang together — people who score low on one measure tend to score low on the others, and vice versa. Psychologists sometimes refer to this similarity as general intelligence.

Or g.
It’s still not clear what in the brain accounts for intelligence. Neuroscientists have compared the brains of people with high and low test scores for clues, and they’ve found a few.

Brain size explains a small part of the variation, for example, although there are plenty of people with small brains who score higher than others with bigger brains.

Other studies hint that intelligence has something to do with how efficiently a brain can send signals from one region to another. …

Hundreds of other studies have come to the same conclusion, showing a clear genetic influence on intelligence. But that doesn’t mean that intelligence is determined by genes alone.

Our environment exerts its own effects, only some of which scientists understand well. Lead in drinking water, for instance, can drag down test scores. In places where food doesn’t contain iodine, giving supplements to children can raise scores. …

But in the past couple of years, larger studies relying on new statistical methods finally have produced compelling evidence that particular genes really are involved in shaping human intelligence.

“There’s a huge amount of real innovation going on,” said Stuart J. Ritchie, a geneticist at the University of Edinburgh who was not involved in the new study.

… To her surprise, 52 genes emerged with firm links to intelligence. A dozen had turned up in earlier studies, but 40 were entirely new.

But all of these genes together account for just a small percentage of the variation in intelligence test scores, the researchers found; each variant raises or lowers I.Q. by only a small fraction of a point. …

In the new study, Dr. Posthuma and her colleagues limited their research to people of European descent because that raised the odds of finding common genetic variants linked to intelligence.

But other gene studies have shown that variants in one population can fail to predict what people are like in other populations. Different variants turn out to be important in different groups, and this may well be the case with intelligence.

“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. …

Here’s the abstract of the new paper:
Genome-wide association meta-analysis of 78,308 individuals identifies new loci and genes influencing human intelligence

Suzanne Sniekers, Sven Stringer, Kyoko Watanabe, Philip R Jansen, Jonathan R I Coleman, Eva Krapohl, Erdogan Taskesen, Anke R Hammerschlag, Aysu Okbay, Delilah Zabaneh, Najaf Amin, Gerome Breen, David Cesarini, Christopher F Chabris, William G Iacono, M Arfan Ikram, Magnus Johannesson, Philipp Koellinger, James J Lee, Patrik K E Magnusson, Matt McGue, Mike B Miller, William E R Ollier, Antony Payton, Neil Pendleton, Robert Plomin, Cornelius A Rietveld, Henning Tiemeier, Cornelia M van Duijn & Danielle Posthuma

Nature Genetics (2017) doi:10.1038/ng.3869 Received 10 January 2017 Accepted 24 April 2017 Published online 22 May 2017

Intelligence is associated with important economic and health-related life outcomes1. Despite intelligence having substantial heritability2 (0.54) and a confirmed polygenic nature, initial genetic studies were mostly underpowered3, 4, 5. Here we report a meta-analysis for intelligence of 78,308 individuals. We identify 336 associated SNPs (METAL P < 5 × 10−8) in 18 genomic loci, of which 15 are new. Around half of the SNPs are located inside a gene, implicating 22 genes, of which 11 are new findings. Gene-based analyses identified an additional 30 genes (MAGMA P < 2.73 × 10−6), of which all but one had not been implicated previously. We show that the identified genes are predominantly expressed in brain tissue, and pathway analysis indicates the involvement of genes regulating cell development (MAGMA competitive P = 3.5 × 10−6). Despite the well-known difference in twin-based heritability for intelligence in childhood (0.45) and adulthood (0.80), we show substantial genetic correlation (rg = 0.89, LD score regression P = 5.4 × 10−29). These findings provide new insight into the genetic architecture of intelligence.

I’m aware of two big Genes-IQ pushes going, often by the same people, of putting together results from previous studies to get up to the sample sizes needed. This one works with smaller sample sizes but with a better dependent variable, IQ score.

The other one uses a murkier dependent variable, educational attainment (years in school), a number that is commonly asked on medical research studies, but samples sizes are about an order of magnitude larger. This other effort expects to reach a sample size of one million this year.

And here’s Dr. James Thompson in the Unz Review explaining the recent (non-genetic) paper on estimating IQs from brain scans.

[Comment at Unz.com]