A recent scientific discovery may help fill in some of the remaining gaps in our understanding of human evolution (see here details). 

Scientists from the United States, Belgium and France identified 49 "human accelerated regions" (HARs) showing a lot of genetic activity.
In the most active, identified as HAR1, they found 18 out of the 118 nucleotides had changed since evolutionary separation from chimps some 6 million years ago, while only two had changed in the 310 million years separating the evolutionary lines of chimps and chickens.

"Right now we have very suggestive evidence that it might be involved at a critical step in brain development, but we still need to prove that it really makes a difference," team leader David Haussler from the Howard Hughes Medical Institute and the University of California, Santa Cruz told Reuters.

This research may also hold the key to understanding why George Bush often seems more chimpanzee-like (physically, verbally, and mentally) than presidential (see here). You see, his brain may simply be less evolved.  How ironic given that Bush himself has suggested that the "jury is still out on evolution" (see here).  Perhaps this kind of willful ignorance is itself the result of a deficient HAR1!