Comment by milesrout

The Flynn effect is about the change in measured intelligence through the 20th century. It tells us precisely nothing about the difference in intelligence between the 13th century and today, let alone going back before the Bronze Age Collapse or agriculture.

A large part of the Flynn effect may be due to reductions in environmental pollutants, which would mean it would be a reversal of the effect of the industrial revolution. Or it may have been due to people being much more used to taking tests. Or it may be due to nutrition. It is unlikely to be due to modern education forcing people to "learn to reason abstractly from an early age" because schools don't require students to learn to reason abstractly from an early age.