Sleepy time at Sibudu. Researchers have found microscopic evidence (inset) of 77,000-year-old bedding at this South African cave. "Early to bed and early to rise, makes a man healthy, wealthy, and wise," wrote Benjamin Franklin in his Poor Richard's Almanack. That may have held true a couple of hundred years ago, but when it comes to our ancient human ancestors, researchers don't know much about how—or even where—they slept. Now a team working in South Africa claims to have found the earliest known sleeping mats, made of plant material and dated up to 77,000 years ago—50,000 years earlier than previous...