- •National fertility and country-level general intelligence (G) negatively correlate.
- •The frequencies of 8 SNPs that predict IQ also negatively correlate with fertility.
- •Both findings are associated with Jensen effects.
- •The SNP metagene negatively predicts fertility, when controlled for HDI.
- •Global G should decline due to selection by − 0.253 points per decade.
Genetics seem to be keeping K-families smaller than r-types’, enough to moderately provision each child with high investment parenting. However, the effect is mild, suggesting it prevents Malthusian exhaustion.