So then you would expect to see very similar results from similar sized interbreeding populations?
There are plenty of such examples in the world. It would be quite interesting if this study compared comparable samples, but the results would likely lead to more questions than answers.
Well, in modern times, I'm not sure that we have a comparable sample population. And even then, it depends on what traits are being selected for. Intelligence is only one trait among many, and the benefits to a trait are at least partially determined by the environmental needs.
In ancient times, however, I would submit that the branching off of the original populations for the various races of man show what happens when small isolate population breed endogamously.