I am quite elderly now, but have had more experience with people of different races than most. I therefore feel my opinion is worth considering.
In my time I have worked under, with, and over people of several different nationalities - a lot of the time in a teaching role.
If you put two people side by side there is no denying that there are differences that are visible and invisible due to their genetic heritage. One of those differences will be intelligence. However, for any difference you chose there will be a wide range and I have found that these ranges are so wide and the overlap so great that I doubt that the average intelligence, as demonstrated to me, is much different for any chosen group.
Because my experience has been mostly teaching technical matters all my foreign students were well educated before coming into my hands. This raises another question in my mind. What do we mean by intelligence? IMO if the only reason for lack of knowledge is lack of education then that does not prove lack of intelligence. If the ability to learn was always there that person was always intelligent. If there is a genetic link to that ability then it will be passed on in the usual way. Don't assume a person is not intelligent just because the life he has led results in a lack of knowledge!