DURHAM, NORTH CAROLINA—After measuring more than 1,400 ancient and modern skulls, Robert Cieri of the University of Utah argues that human skulls changed in ways that indicate testosterone levels dropped some 50,000 years ago, at the same time that human culture blossomed. “The modern human behaviors of technological innovation, making art and rapid cultural exchange probably came at the same time that we developed a more cooperative temperament,” he told Science Daily. Heads became rounder without heavy brows, which can be traced to lower levels of testosterone, according to Steven Churchill, an anthropologist at Duke University who supervised Cieri’s undergraduate work. “If prehistoric people began living closer together and passing down new technologies, they’d have to be tolerant of each other. The key to our success is the ability to cooperate and get along and learn from one another,” Cieri explained.
