The comparative data suggest that during the evolutionary process, humans somehow altered the process of gene expression in their brains, accumulating expression differences at least five times faster than chimpanzees and distancing themselves from their nearest cousin. A similar trend appeared when the scientists examined differences in brain protein levels.
To determine if the differences between humans and chimps were indeed more than expected between such closely related species, the researchers also analyzed gene and protein expression in two mouse species that are about as genetically different from to each other as humans are to chimps. They found fewer differences in gene expression levels among the mice, further suggesting that the human-chimp discrepancy marks a special evolutionary process
Whatever could they mean by 'special evolutionary process'? Didn't they have a hard time explaning how known mutation rates for both species could have produced the differences already observed between the two? How much bigger is this problem now?