You state in your News story on genetic differences between humans and other species (“Mix and match: the hunt for what makes us human” Nature 443, 8; 2006) that research is beginning to pin down genes that “evolved rapidly during the transition from chimps to people”. No such transition occurred, of course, because chimpanzees are not human ancestors; they have been evolving for exactly the same amount of time.
A mutation is, in principle, just as likely to have occurred in the chimpanzee lineage as in the human lineage, during the time since their common ancestor lived. There is no way to discover from any comparison of the two species which is the case.
To determine the evolutionary history of a trait and its genetic basis, it is necessary to make phylogenetic reconstructions based on comparisons among many species. Chimp–human differences make good headlines, but tell us little about how human uniqueness evolved.