IQ and Inbreeding

I was curious about the literature on inbreeding depression of IQ. A literature search led me to conclude two things:

- This is not a sexy field. A lot of the results are old.

- The range in depression for first cousin marriages seems to be on the order of 2.5 to 10 IQ points. In other words ~0.15 to ~0.65 standard deviation units of decline in intelligence.

-- Razib Khan

from "Cousin marriage can reduce I.Q. a lot"

Quoted on Sun Jul 22nd, 2012