Violent dreams may hint at why dreaming evolved, researchers say

Twenty years ago, scientists discovered a bizarre disorder whose victims act out their dreams while asleep, often hurting themselves or their spouses in the process.
One patient kicked a hole in his bedroom wall, according to a paper published in a medical journal. Another tried to jump out a window. A third fired an unloaded gun, a fourth attempted to set his bed on fire. Still others tried to choke their wives.