Kong, Augustine et al. – 2016 – Selection against variants in the genome associated with educational attainment
This paper makes the case that there has been a decline in the prevalence of genes increasing propensity for more education (POLY EDU) in Iceland from 1910-1975.
Here are some of the key points:
- The main mechanism was greater age at first child, not total number of children (i.e. the clever are breeding more slowly).
- As in many such studies, the effect is stronger for women.
- One allele associated with more children and having them earlier also tags a haplotype associated with “reduced intercranial volume” and neuroticism: “… thus a striking case where a variant associated with a phenotype typically regarded as unfavorable could nonetheless be also associated with increased “ fitness” in the evolutionary sense.“
- The decrease in POLY EDU prevalence was faster earlier this century, but this is an artifact of the higher survival schedules of people with a higher propensity for education (i.e. tying in with the well known finding that higher IQ is associated with higher life expectancy). The decline from 1940 onwards becomes linear, and is a better measure of estimating the change of the average polygenic score over time.
- It is estimated that is POLY EDU declining by 0.010 SUs per decade, but this rises to 0.028 SUs per decade because the measure captures only a fraction of the full genetic component of education attainment (POLY FULL).
- The trends in POLY FULL are estimated to be causing a decline of 0.30 IQ points per decade.
- The authors note that this has entirely canceled out and then some by the Flynn effect, but it could still have “a very substantial effect if the trend persists for centuries.”
Many other studies indicate that the FLynn effect has ended or gone into reverse across the developed world around the 2000s by the latest.
If it’s a permanent plateau, we could be seeing 3 IQ point declines per century. Extend that out for two or three centuries, add some more Third World immigration, and you get the 1 S.D. IQ decline that I posited for the Age of Malthusian Industrialism aka the business as usual scenario.