If something like meditation practice can affect the relative sizes of different portions of the brain over the course of a lifetime, I suppose the amount of abstract thought we engage in probably means our modern brain differ slightly from those 20,000 years ago, but is the change at a genetic level? I know very little of epigenetics. Could the acquisition of language have caused changes at a genetic level? If you're interested in an attempt at a unified theory describing the evolution of consciousness, check out Ken Wilber's work. He's a brilliant philosopher with a background in biology who has now gone a bit nutty.