Even if the average IQ was 150 (by today's standards), there would still be a large range of values with a significant variance. There probably wouldn't be that much of a difference at all for this reasom alone, regardless of th further fact that the progress of a civilisation is not measured solely by its members ability to recognise patterns, which is all that an IQ tests involves.
In my opinion, the growth of a civilisation is not just measured in terms of political and economic systems whoch could probably be proved upon by highly intelligent people, but by its ethics and how they are practiced. Alas, deotological ethics does not work, and there is a lot more to a civilisation than what IQ cna measure.