As a species, our brains are shrinking. For a long time (understatement of the year, haha) our brains were growing, but over the last 20,000 years we've lost about 1 tennis ball size chunk of brain. Below is a three-page article discussing the different theories as to why this is happening. Personally, I think it is a mixture of Justin Beiber and Rebecca Black's poisonous "music" seeping into peoples' heads through the airwaves. Maybe the brain isn't really shrinking; maybe different parts of it are just committing suicide.