Direct Evidence that Intelligence is Half Genetic: New Hope for Closing the Achievement Gap?

Many people believe that intelligence, like most human characteristics, is affected both by genes and environment.

Indeed, studies of fraternal and identical twins, especially those of identical twins raised apart, summarized in the chart above and, for example, THIS, provide strong evidence that intelligence is roughly half genetic. A survey of 661 experts on intelligence found that the large majority believe intelligence has a significant genetic component.

But there hasn't yet been an analysis of actual genomes to prove that...until now.

THIS study of 3,511 people's genomes was published on the prestigious Nature.com last month but remains largely unreported by the media. The abstract reports, "Our results unequivocally confirm that a substantial proportion of individual differences in human intelligence is due to genetic variation."

What are the implications?

The bad news

This has to be a blow to educators and social policymakers, who, for a half century now, have been betting billions of tax and charity dollars that the achievement gap could be significantly reduced or eliminated by redistributing resources to improve the environments of low-achieving children and adults by more spending on education, job training programs, self-esteem programs, etc. But just as in a long-distance car race, tuning-up a VW Bug that's running miles behind a Porsche doesn't make it likely to catch up, it appears ever less likely that tuning-up low achievers' environment will close the achievement gap to the extent we all hope it will.

Indeed, that study may help explain why, despite massive expenditures on the widest range of such programs, from Head Start (which, in the definitive metaevaluation, alas has been found to have no impact on the achievement gap) to Stop Drop, the achievement gap remains as wide as ever.

Especially in this era of massive federal, state, and local deficits, we might want to ask ourselves how wise is it to continue to reallocate billions of dollars from gifted education to special education, from regular education to compensatory education. Indeed, our core federal education mandate, No Child Left Behind, and other major programs such as Title I, plus much nonprofit funding do that.

The good news

The good news is that the Nature study would seem to point to a new direction and new hope for reducing that achievement gap. In light of that study, the next steps would seem to be to discover the specific genes responsible for intelligence (something China is already doing) to develop a safe and ethical way to replace defective genes and then making available, on a purely voluntary basis, the option to have that gene therapy so prospective parents could help ensure that their kids don't start life with a genetic strike or two against them.

To ensure that option doesn't exacerbate the gap between rich and poor, it should, like most medical services, be fully covered under MediCal (the free health care program for the poor,) and under ObamaCare. In addition, special outreach to low-income communities should be provided, emphasizing both the therapy's availability and its being completely optional.

I would imagine that the therapy would most benefit families of multigenerational low achievement. If my parents were low achievers, I were a low achiever, and now I heard that intelligence was half genetic and there was a free, safe, and effective therapy that would improve my children's chances of having high intelligence and, in turn, be more likely to be successful in school and in career, I'd sign right up.

Here is the study's abstract.

Genome-wide association studies establish that human intelligence is highly heritable and polygenic

G Davies, A Tenesa, A Payton, J Yang, S E Harris, D Liewald, X Ke, S Le Hellard, A Christoforou, M Luciano, K McGhee, L Lopez, A J Gow, J Corley, P Redmond, H C Fox, P Haggarty, L J Whalley, G McNeill, M E Goddard, T Espeseth, A J Lundervold, I Reinvang, A Pickles, V M Steen, W Ollier, D J Porteous, M Horan, J M Starr, N Pendleton, P M Visscher and I J Deary

Abstract

General intelligence is an important human quantitative trait that accounts for much of the variation in diverse cognitive abilities. Individual differences in intelligence are strongly associated with many important life outcomes, including educational and occupational attainments, income, health and lifespan. Data from twin and family studies are consistent with a high heritability of intelligence, but this inference has been controversial. We conducted a genome-wide analysis of 3511 unrelated adults with data on 549 692 single nucleotide polymorphisms (SNPs) and detailed phenotypes on cognitive traits. We estimate that 40% of the variation in crystallized-type intelligence and 51% of the variation in fluid-type intelligence between individuals is accounted for by linkage disequilibrium between genotyped common SNP markers and unknown causal variants. These estimates provide lower bounds for the narrow-sense heritability of the traits. We partitioned genetic variation on individual chromosomes and found that, on average, longer chromosomes explain more variation. Finally, using just SNP data we predicted ~1% of the variance of crystallized and fluid cognitive phenotypes in an independent sample (P=0.009 and 0.028, respectively). Our results unequivocally confirm that a substantial proportion of individual differences in human intelligence is due to genetic variation, and are consistent with many genes of small effects underlying the additive genetic influences on intelligence.