I find this stress on "IQ" to be a little uncomfortable to me. As I have tried to argue before, IQ tests are basically a test of what I would call "cultural competency". Usually, this involves such things as literacy, ability to understand and manipulate mathematical symbols, etc. Most IQ tests only sample across a fairly narrow range of skills. For example, I might score relatively highly on literacy, but my skills in the trades such as carpentry, electronics, plumbing, pest-control, IT support, etc. may not be all that well developed. An IQ test may be a very good measure of my literacy, but not very good at measuring these other fields and their related knowledge demands.
I suppose one can argue that a high level of "general cultural competency" throughout the population correlates to a "successful society." Still, that is slightly different than saying that a high level of "intelligence" correlates with a successful society. Intelligence is more of an innate attribute. Cultural competence, more of an acquired attribute. Obviously, a high innate level of intelligence may be of help in more quickly acquiring a high level of cultural competence such as literacy. Still, intelligence is not the only factor. Other things such as education, parental attention, access to a wide variety of information media, personal health, nutrition, etc. are also important factors.
Just my two cents for what it might be worth to the rest of the discussion.