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