But if his idea were correct, discovering when the body louse diverged from the head louse would provide a rough date for when people first invented and wore clothing. The subject was anything but frivolous: donning a garment is a complicated act. Clothing has practical uses—warming the body in cold places, shielding it from the sun in hot places—but it also transforms the appearance of the wearer, something that has proven to be of inescapable interest to Homo sapiens. Clothing is ornament and emblem; it separates human beings from their earlier, un-self-conscious state. (Animals run, swim, and fly without clothing, but only people can be naked.) The invention of clothing was a sign that a mental shift had occurred. The human world had become a realm of complex, symbolic artifacts.
Charles C. Mann, excerpt from his piece in Orion Magazine called “State of the Species”