Sorry if I've missed some of the discussion, but may I add that brain size
has actually shrunk in the last 10,000 year since Neolithic foods came
along. This indicating that evolution was increasing brain mass, and then
Neolithic diet has been reversing it. i.e. caveman were smarter because they
were feeding their brains better!
Reference: Christopher B. Ruff et al, Body mass and Encephalization in
Pleistocene Homo (letter)Nature Vol 387 8 May 1997 pp173-176
The relevant data:
Years ago. Cranial capactiy (cc)
current  worldwide        1349
current Pecos Peublo  1308+/-23
10000-21000                1466
21000-35000                1517
36000-75000                1498
90000                             1501
100000-150000            1354
200000-300000            1186
400000-500000            1090
600000-1,150,000         856
1,200,000-1,800,000     914

I'm aware that the number of convulutions on the surface of the brain is as
important as its size in determining intelligence, but have no data on this.

So, forget about smart drugs. If you want your brain to work better, or your
kids to be smarter, consider the paleolithic diet as your best option.

Ben Balzer