Well, that was a different reference in GP's post. You can go read it. Heritability is definitely a thing, but far from the only thing and it isn't simple Mendelian inheritance - there are many components to intelligence that reflect differently in gene transfer and so while you can see a correlation in specific individuals and their immediate ancestors there are lots of exceptions and its probably a mirage - if seen at all - in any large demographic. See my other comment on the problems with eugenics in this thread.