The human brain has undergone dramatic evolutionary advances. Today, however, many people suffer from strokes -- the rupturing of blood vessels in the brain. The truth is, humans suffer from strokes because brain size increased too rapidly during the course of human evolution. The blood supply to our brains increased threefold during the last 2.5 million years, but the walls of our blood vessels didn't adjust to this change and remain fragile. In addition, changes in lifestyle and dietary habits continue to cause damage to blood vessels. The hidden secrets of strokes in light of evolution are explored in this episode.