Uh, from that link.
http://en.wikipedia.org/wiki/Religi...iaviewer/File:LynnHarveyNyborg-Atheism-IQ.svg
Looks like the largest concentration of countries with average IQs over 100 is 30% Atheist or less.
In any case, correlation != causation, all that article states is that the subject is highly controversial and unproven. For instance it's quite possible that a higher IQ motivates one to more extensively challenge the ideas posed by religion thus resulting in a larger percentage of Atheists, and that if people of lower IQs had equivalent motivations they might very well exhibit the same tendency.
In any case I've seen this argument stated as fact by atheists everywhere, and frankly all it shows is how the advantage of their supposed greater average IQ pales in comparison to the human need to justify one's beliefs.
Full disclosure: I'm philosophically Taoist and am about as nonreligious as you can get, and I find it remarkable how quickly Atheists adopt controversial arguments as facts when it make them feel justified. I suppose it's a notch better than adopting mythical fairy tales as fact and justification, but the two behaviors are remarkably similar.
Atheism at large is fast becoming the religion of the anti-religious who have been mistreated in some way by religious people. At the end of the day I don't get why the debate on either side is worth so much effort, must be compensating for something somewhere.