For most of human history, sleep was social, Benjamin Reiss argues in Wild Nights: How Taming Sleep Created Our Restless World, reports New Republic.

During the Industrial Revolution, a new kind of “sleep dogma” took hold, one immediately recognizable to many Westerners today. The new “sleep norms” included “sleeping in private” and “consolidating one’s sleep at night”—the eight hours we now think of as a gold standard for proper rest.