There’s a new paper out on how the frequency of variants that affect educational achievement (which also affect IQ) have been changing over time in Iceland. Naturally, things are getting worse.
We don’t have all those variants identified yet, but from the fraction we do know and the rate of change, they estimate that genetic potential for IQ is dropping about 0.30 point per decade – 3 points per century, about a point a generation. In Iceland.
Sounds reasonable, in the same ballpark as demography-based estimates.
It would be interesting to look at moderately recent aDNA and see when this trend started – I doubt if has been going on very long.
This is the most dangerous threat the human race faces.