Fortunately I have read about some controversial studies done on eugenics, so I hope I can answer this.
First of all, there has been no comprehensive IQ exam that surpasses linguistic problems. Say GMAT, it is basically considered an IQ test. However, it is completely in English. Would it mean that a person who has no knowledge of English, or is illiterate has no IQ?
Secondly, if we see how the IQ of animals, especially dogs is determined. People love to say one breed of dog has higher IQ than the other, but in the end it is always conceded that what the dog comprehends, and how well it does so, depend on the need and adaptability of the dog.
Similarly, a peasant who is an expert at determining what are the requirements of the soil, might have higher IQ for his work, than that of a Brahmin who can derive the value of pi by the number of trips a certain boat has to make to perform perfect banking.
This guy, Steve, takes memory and calculative abilities to measure the IQ of certain demography. But that's all that Brahmins have done since the beginning. Just as the Ashkanazi Jews had to do bookkeeping for generations since they had no right to own land. It simply means these particular communities are simply a little more skillful in certain areas than are others.
Say, if I am a champion chess player, and teach my son the same at young age, he will certainly end up being a better than average player. It does not mean a wrestler's kid would perform any less if taught at the same age by a skilled chess player.
Btw, congrats on Hou Yifan ;-)