See: https://www.researchgate.net/publication/325704105_Flynn_effect_and_its_reversal_are_both_environmentally_caused https://www.researchgate.net/publication/

See: https://www.researchgate.net/publication/325704105_Flynn_effect_and_its_reversal_are_both_environmentally_caused https://www.researchgate.net/publication/325704105_Flynn_eff... Although there is still one possible genetic cause, which is people (both women and men; in fact, some studies show the effect is stronger for men: https://www.nature.com/articles/gim200868 https://www.nature.com/articles/gim200868) having children later in life.