Sometime between 7-6 million years ago, our primate ancestors stood up and began to walk on two legs. A defining moment along the winding evolutionary roads to becoming human, this is the feature researchers use to distinguish hominins from other apes. Although why it occurred remains an intriguing mystery. By about 2 million years ago, we became fully bipedal, but there were many steps along the path to get us there. Some of these steps still elude our fossil records, but a new study analyzing the remains of a female Australopithecus that researchers nicknamed Issa, has found another. "Issa walked...