Interesting quote from that link

To be sure, there has been a reduction in the average brain size in South Africa during the last 10,000 years, and there have been parallel reductions in Europe and China -- pretty much everywhere we have decent samples of skeletons, it looks like brains have been shrinking. This is something I've done quite a bit of research on, and will continue to do so, because it's interesting. But it is hardly a sign that ancient humans had mysterious mental powers -- it is probably a matter of energetic efficiency (brains are expensive), developmental time (brains take a long time to mature) and diet (brains require high protein and fat consumption, less and less available to Holocene populations).

This still requires some explanation although not to the level of the 150 IQ lineage.