The Upstairs and Downstairs Brain

Our amygdala (pronounced uh-MIG-duh-luh) is about the size and shape of an almond and is part of the limbic area, which resides in the downstairs brain. The amygdala’s job is to quickly process and express emotions, especially anger and fear. This little mass of gray matter is the watchdog of the brain, remaining always alert for times we might be threatened. When it does sense danger, it can completely take over, or hijack, the upstairs brain. That’s what allows us to act before we think...

 A lot happens in 100k Years of Evolution

Inside my skull is a brain that was designed to exploit the conditions of an African savanna between 3 million and 100,000 years ago. When my ancestors moved into Europe (I am a white European by descent) about 100,000 years ago, they quickly evolved a set of physiological features to suit the sunless climate of northern latitudes: pale skin to prevent rickets, male beards, and a circulation relatively resistant to frostbite. But little else changed: Skull size, body proportions, and teeth ar...