Comment by ghgdynb1

People have definitely gotten smarter. Here’s a small case which might help illustrate how this happens in general: We know infection with hookworms and other soil-transmitted helminths will do nasty things to the intelligence of the patient, especially for children. Since humanity got rich enough to build sewer systems and shoes and anti-parasitic drug companies, soil transmitted helminths have become a lot less of a problem (and the same goes for their cognitive effects).