Yes. Intelligence is determined by the DNA we inherit and may be reduced by encounters with the environment (disease, toxins, and head trauma). That’s the whole story. Notice that there is no mention of education.
IQ and educational achievement (EA) are strongly and positively correlated. The direction of causation is from intelligence to EA. We go to school to learn important things, such as language, math, and science. Learning these things does not make us more intelligent—it makes us more educated.
When geneticists finally discovered how to identify the associations between single nucleotide polymorphisms and polygenic traits, they found SNPs that relate to EA.
It has been known for a very long time that intelligence is highly heritable. Using multiple, independent, methods of measuring intelligence, the heritability of IQ turns out to be above 80% and is probably more accurately stated as 85% in developed nations. (see page 51 of the reference below) Psychometric g is up to 91% heritable.
Haier, R. J. (2017). The Neuroscience of Intelligence, Cambridge University Press.
The problem was (for many years) that the genes that were assumed to account for intelligence were missing. I heard Robert Plomin’s presentations about every two years (ISIR conferences). He told us that the methods they were using could not miss genes with a 1% effect size, but none had been identified. Then, one morning in Albuquerque, I had a chat with James Lee, before he was scheduled to present his paper. He said that, using educational achievement measures, a large number of single nucleotide polymorphisms were identified from his genome wide association study (GWAS). I was impressed, but had no idea of the gravity of this breakthrough. When the data were used to compare with similar SNP identifications for intelligence, it turned out that the educational achievement results were more predictive of intelligence than of educational achievement. Consequently, researchers merged the two sets of genomes to produce one with 1.1 million individual genomes. Using this, they identified 1,271 SNPs that were associated with high intelligence. By the next time I saw James, the GWAS results had become a recognized breakthrough. For details of how GWAS is done and how the results are used to create polygenic scores, capable of measuring intelligence, see Robert Plomin - Blueprint: How DNA Makes Us Who We Are, Penguin Books Ltd., 2018, ISBN 9780241282076.
[It is both important and interesting to understand that the SAME SNPs that are associated with EA are also associated with intelligence and have larger effect sizes for intelligence.]
The SNPs that determine intelligence have an average effect size of 0.01% (tiny). That tells us that the number of SNPs that define individual intelligence is in the tens of thousands.
Because we now have the key, the polygenic scores can be used to measure IQ, even before birth. See Using DNA to predict intelligence; Sophie von Stumm, Robert Plomin; Intelligence 86 (2021) 101530. In Blueprint, Plomin commented that “We were looking for gold nuggets, but we found gold dust.”
Using polygenic scores:
Published Genome Wide Association Studies (GWAS), reporting the presence of alleles exhibiting significant and replicable associations with IQ, are reviewed. The average between-population frequency (polygenic score) of nine alleles positively and significantly associated with intelligence is strongly correlated to country-level IQ (r = .91). Factor analysis of allele frequencies furthermore identified a metagene with a similar correlation to country IQ (r = .86). The majority of the alleles (seven out of nine) loaded positively on this metagene.
A review of intelligence GWAS hits: Their relationship to country IQ and the issue of spatial autocorrelation; Davide Piffer; Intelligence 53 (2015) 43–50.
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