In 2015, archaeologists working at a cave in southwestern Germany found an enigmatic perforated baton in a cave called Hohle Fels. It was a near-perfect match for an artifact found in 1983 in a cave down the road. Carved from single pieces of mammoth ivory, the Hohle Fels baton—roughly 20 centimeters long, about the length of a large paperback book—had multiple holes with spiraling grooves around the openings. Similar objects have been found elsewhere in Germany and in nearby France, often made from ivory or antler. They date from the last ice age, more than 35,000 years ago, a time...