STONY BROOK, NEW YORK—The invention of the bow and arrow triggered the growth of increased levels of social complexity wherever it was adopted, according to biologists Paul Bingham and Joanne Souza of Stony Brook University. They argue that the technological revolution of the bow and arrow gave social groups a safe and effective way to coerce uncooperative individuals into compliance, or to encourage them to leave. A review of archaeological data in North America by John Blitz and Eric Porth of the University of Alabama supports this “social-coercion hypothesis.” They say the invention of the bow made hunters and warriors more efficient, and eventually led to population increases and the metropolises of the Mississippian era.