Flowers for Algernon!
So the assumption is that there is a "brain peak" that is mysteriously reached when all the genes are right?
That sounds like a pretty bizarre idea.
And that point would be reached in the times of classical Greece?
Most bizarre. Note that the ancients had exactly the same problems as we do today: retarded politicians, stupid wars, neocons, fascism, cities going from "money for everything" to "no more money, dude", throwing money out of the window to erect stuff in honor of "Gods", slavery, killing of critical philosophers, racism, bad social systems, destruction of the environment via goat herds. The evidence for particulary high intelligence is, I would say, not that great.
An individual's à priori penchant for "high intelligence" (which btw. may go completely unnoticed as he may be reduced to a lifetime of cotton-picking) is bound to be a probability density function in a very high-dimensional space of genetic variations. There is no à priori reason to suppose that the population ensemble was clustered at a peak point and is now fanning out into "lower" regions.
Now, brain "malformations" are generally of deleterious consequence, which would at first glance tend to support the idea that the modern brain is somehow "exactly what is needed" or that it is very fine-tuned (For what? For rapid learning and effective cooperation in a environment in which other brains of the same power are bound to eat its lunch I suppose. How does that translate into solving QCD Lagrangians in one's sleep? Beats me.).
Anyway -- one would like to see the statistical distribution of "genetic brain anomalies" that are of no visible consequence (although they may shift perceptions or behaviour) and "genetic brain anomalies" that actually have advantageous consequences (we would however be reduced to the relatively simple tests for "advantageousness", like IQ tests and game solving. Psychopathy could be considered an "advantageous" trait, as you f*ck everyone with no remorse, right?). This would give us some idea of whether the current brain is in some very special "peak position" and whether genetic variations push it "down" that peak or whether things are more reasonable with variations exploring a hilly landscape.
To your MRI scanners!
Meanwhile, I'm waiting for ROTM.