How Our Brains Got Big and Our Penises Lost Their Spines
The relationship between humans and chimpanzees, thought to be pretty close in evolutionary terms, now comes down to a number: 510. Those are the genetic elements, in key areas of the genome, that differ between the two species. Surprisingly they aren’t 510 pieces of DNA that we have and chimps don’t. It’s actually the other way around. But our loss, paradoxically, is also our gain. The absence of one piece may have led to a feature that anthropologists have been struggling to explain for centuriesâ€”our big, complicated, non-chimplike brain.