Researchers have discovered in the Kenyan desert what they believe to be the oldest humanlike footprints—several trails of them laid down in what was a muddy riverbank 1.5 million years ago. Ancient footprints are an extremely rare discovery because conditions must be perfect for them to be preserved. Furthermore, footprints can tell us many things about a specimen that a skeleton cannot, such as gait and weight distribution. “They were probably just as efficient at walking upright as we are,” said one of the archeologists of the creatures. The prints also suggest this ancestor was more human than ape, with large, straight toes built more for running than for grasping the branches of trees.