My fav hypothesis - increasing CO2 toxicity: https://pubs.rsc.org/en/content/articlelanding/2025/va/d5va0...

If an IQ of 100 represents the average when measured, then they can/may only fall for some cohorts.

Ans.: b/c people today are not as well educated as in the past.

Meanwhile, paywall! Could we have a free link to the article, please?