Reports (eg) of genetic evidence that the human brain evolved usually fast may be exaggerated – see this very thorough post at language log (thanks to Cosma for the heads up).
This quote seems pretty typical of the media reports:
Humans went into evolutionary overdrive as their brains developed, sending them on a path that set them apart from other animals, scientists believe
And you can understand the general yearning for signs of human uniqueness. Despite this there is no structure, or chemical, in the human brain that isn’t found in other species – and, it seems, even the pace of genetic change associated with human brain evolution isn’t unprecentedly fast (languagelog cites a cell adhesion protein in the zebrafish, and the SARS virus as just a couple examples of higher rates of change).
Although it isn’t unprecendented, the rate of genetic change in human and primate nervous-system evolution is at least fast – (maybe especially fast for such complex structures? I don’t know, I’ve no expertise in this) – and who would argue that even though there is a continuity in the building-blocks of the human brain there has been some sudden leap in it’s emergent properties?
(Terrence Deacon, in his Symbolic Species argues that this is due to co-evolution of the brain and langauge – which is by-the-by mostly except that it allows me to mention a book which I will be compulsory reading when I am king of the world.)
We don’t need genetic evidence of human uniqueness (indeed, the way our species behaves it might be more helpful to focus on our similarities to the rest of nature), but it’s great to have some qualitive figures on the rate of evolution of the human brain’s genetics – and, in a different way, it’s equally great to have blogs like languagelog which give such an informed and accessible critique of the research, unlike most of the traditional news media – great stuff!