We do know that Lucy and her australopith colleagues, while persistently hanging in for more than 2 million years, were nothing much more than bipedal apes with chimp-sized brains. But some time earlier than 2.5 million years ago, some creature that may not have been all that different from Lucy gave rise to a creature similar in stature-about three and a half feet tall, maybe four feet-but with a noticeably larger brain. This was Homo habilis, and their kind or kinds (generally presumed to be the ﬁ rst members of the genus Homo) were possessed of brains ranging from 510 to 750 cubic centimeters, the mean volume being 635. Some evidence recently came to light that this remarkable growth in brain volume might have been helped along by a chance mutation in a single gene of the creature that was becoming Homo habilis. Geneticists announced in the summer of 2006 that they have found a region of human DNA associated with the brain that anciently changed very quickly.