[names_are_hard]

> If it were true, then decline wouldn't have begun in the 19th or 20th century but around the time that property and currencies emerged.

Why? Can you elaborate on that? Did the emergence of property and currency cause a negative correlation between intelligence and number of offspring?

[vintermann]

I think there's so much ill-founded assumptions in eugenics BS that it's hard to know where to start, but as a genealogist, I can personally verify that upper or middle class, wealthier people, presumably the sort eugenicists identify with, clearly had at least a 2-3 generations head start on the demographic transition where I come from.

There are other trends, there's always some groups of people who started having fewer kids earlier or later for reasons not obviously related to class - but class is the big one.