[From many - one.]

I think what they were trying to say, in a particularly garbled way, is not that Jews in Europe got smarter, but that less smart Jews died off, raising the average and shortening the range.
Instead of 50-150 it would now be 75 to 150 because from 50 to 74’s died off disproportionately.

[dblshot]

“that Jews in Europe got smarter”

Lot of good that did them in 1939-43.

[sportutegrl]

Or that female Jews would only marry, (and thus have children for) males with the intelligence or ability to make a lot of money.