This is what I think about different groups and perceived intelligence.

In Asia, both the spoken and written forms of the languages are incredibly intricate. It makes sense that, culturally, people who have had the kind of mental stimulus throughout their lifetimes that comes with those kinds of languages and ways of writing would develop, collectively, certain capacities for certain kinds of mental functions.

In the case of African, Jewish, and Irish people (and any number of other groups), there is a long tradition of having rich and complex oral histories. In those contexts, it makes sense that, culturally, people who have had the kind of mental stimulus throughout their lifetimes that comes with those kinds of traditions would develop, collectively, certain capacities for certain kinds of mental functions.

I have been told by various people that I have a well developed mental capacity for debate. I know which influences in my developmental years contributed to this capacity and why.

Stimulus is the most important factor in how people develop, mentally. We know this from seeing the difference in people with Downs Syndrome who receive appropriate mental stimulus in their early years as compared to those who are not given much mental stimulus because of prejudices about what people with Downs Syndrom are capable of.

So we see that even in contexts where nature has asserted itself in the genetic makeup of an individual, the nurture factor can still override genetics to a significant degree.

It doesn't follow for people to assume that because one group of people may be more prone to certain illnesses, that would have anything whatever to do with how their brains work.