Scientists have stumbled upon the oldest known fossil of a hand bone that looks a lot like one found in your own hand, though this one is at least 1.84 million years old. Found in Olduvai Gorge in Tanzania, the hominin bone—likely from the pinky of a left hand, reports LiveScience—is remarkable for a couple of reasons: First, it suggests the humanlike hand, which evolved to make and use tools, dates back 400,000 years earlier than scientists previously believed, UPI reports, via the study in Nature. Until this discovery, researchers weren't entirely sure when our ancestors' hands, with curved finger bones for hanging in trees, straightened out. "This bone belongs to somebody who's not spending any time in the trees at all," lead researcher Manuel Domínguez-Rodrigo tells New Scientist. He adds the hominin likely used tools more often than its predecessors.
Second, the bone suggests its owner, an unidentified and possibly unknown human relative, was much taller than other hominins, standing five feet, nine inches. At about 1.4 inches long, the bone is "the same size as the equivalent bone in our hand," says Domínguez-Rodrigo. He believes the species falls somewhere between modern humans and tree-dwellers like Homo habilis—about three feet tall—and Paranthropus boisei on the evolutionary scale. The hominin's size could help explain why early sites in Olduvai include ancient animal carcasses that weighed up to 770 pounds. "I always had trouble understanding how Homo habilis...could efficiently hunt animals that big," the researcher says. "Now, the new discovery shows that a bigger and more modern-looking creature existed at the time these sites were formed." (Some argue early human hands changed little over millions of years.)