Schooling only really started around the 1500s I believe. It would have taken time for that to spread, and I don’t think there was a concept of public education prior to the 1800s. It’s only that point when we all really started to approach problem in a similar manner. With the internet, we’re all now able to solve problem more quickly using available resources. The increased access to info and the average person solving a larger number and wider variety of problems. Seems like the increases in intelligence correlates strongly to the widespread adoption to television, increased with the internet, and will continue to do so at a fairly constant rate as resources and databases improve.