Dear Oksana Tuchina: It is difficult to quantify the average strength of selection propagating advantageous mutations. The way to accurately estimate the average strength of positive selection acting on genome is by inferring the distribution of fitness effects (DFE) of new advantageous mutations. The problem is that DFE is difficult to conjecture because new advantageous mutations are uncommon. More research is necessary to produce accurate estimates of the average strength of positive selection in humans, which will in turn improve the estimates of the amount of adaptive evolution occurring in the human Adaptive evolution in genes linked to brain development is shown by some studies, but such genes are often associated with diseases, for example, microcephaly (ASPM; Mekel-Bobrov et al. 2005) and schizophrenia (DISC1, Crespi et al. 2007).

Your question is very important in search for adaptive evolution in brain genes but there will be ethical issues. If more adaptive evolution are discovered in brain genes in different population, this may show greater intelligence is an adaptively evolved process.

It should be the otherwise. If a gene is under high selective pressure, it is expected to evolve faster, in the sense that there will be more mutations and more polymorphic is  the gene. The one example I can give is the Hb gene, which is under selective pressure because of endemic disease like malaria. As a result there are several variations of haemoglobin in Man.  However Hb gene appears do not show such polymorphism among other non-human world. This should be true in other genes as well, unless if they are influenced by other factors -- favourably and unfavourably.  Even one an also get into population genetics theory, where such questions are answered with more rigour and that is the best. Population genetics is basically theoretical and we only verify or validate with the empirical situations. In case of malaria and HbE it has been well worked out.   

As Artur mentions, lower evolutionary rate can sometimes be interpreted as evidence of negative selection (strong selective pressure against making changes, implying that what currently exists has an important function), while faster evolutionary rate can sometimes be interpreted as evidence of positive selection (what is created is more advantageous than what exists). The problem with using fast and slow evolutionary rate to assign positive and negative selection is in defining what a 'fast' and 'slow' evolutionary rate is. Mutation is a chance event, and some regions of the genome incur more changes than others by chance, even in the absence of any natural selection. We can't say whether slow evolving regions or fast evolving regions are changing faster or slower than chance expectations without defining these chance expectations. People are still debating whether most of the genome is under positive, negative, or neutral selective pressures, so defining the 'expected' rates is challenging. You might start by asking whether genes expressed in the cerebral cortex are changing significantly slower than genes in the genome overall, (and the same for cerebellum, etc.) so that you can at least quantify selection relative to the rest of the genome, but beware neutral variation in mutation rates (which may give a false signal) and multiple test corrections (you're guaranteed to find a significant region if you test enough brain regions).

I was going to type out a detailed response, but remembered work like this from Katie Pollard's group (formerly at my university). You may follow this science news link to the relevant research articles on Pubmed: http://currents.ucsc.edu/06-07/08-28/gene.asp

In short, I think your question is reasonable, and there have been successful attempts to answer it already. I suggest you read the literature.

One point that I wish to emphasize: the rate of nucleotide level DNA sequence change is different from the selection scheme operating on genes. If the rate of DNA sequence change is uniformly high across all codon positions for gene1 and its orthologs, and the change is uniformly low across all codon positions for gene2 and its orthologs, I may infer than Ka/Ks or dN/dS ~ 1 for both cases = case of neutral evolution, but for some reason(s), at an absolute level, gene 1 sequence is changing more rapidly than gene 2. How would gene 1 and gene 2 figure in the answer to your question about relative rates of brain region evolution? Hard to tell, but it would need to be determined on a case-to-case basis, and by adding a layer of experimentation to validate your bioinformatic results.  I suggest you take a look at the HAR1 story from Pollard's group and other such published stories. Good luck!

Dear Colleagues, a selective pressure really depends how important is  a certain gene(s) to human genetic adaptation in certain environment: in one environment such gene can be significant for genetic adaptation, but in new environment during migration of the person -No. For example: Caucasus Dagestan highlanders that are living in traditional for them highland region for about 10 K yeas are very well adapted to own environment -they have less morbidity, high reproduction and long life-span. My long-term study of genetics of highlanders isolated populations indicated that they have a higher mean coefficient of inbreeding and lowr average heterozygosity. Interting fact -among long-livers (older  80)  these both parameters are statistically significantly higher (higher F and Homozygosit) in comparison with rest groups of same isolates.  Dramatic changes in the highlander viability and genomes selections happened when these highlanders villages were in 1944 forcibly moved by Stalin government to the new for them lowland area: in first 2-3 years among them affected by new infections-malaria, typhus etc -about 70% of total migrated and died about 35% (excluded natuaral death). Our study showed that most of those who had aa heavy affectation and deaths -were offspring of closest consanguineous marriage and respectively had more  homogeneous genomes.  This tragic for these indigeneous ethnics example,  clear shows for us -researchers how works genetic adaptation and selective pressure in diverse environment.

Dear all, thank you a lot for your helpful feedback!