It took millions of years for modern humans to evolve from apelike creatures to today’s Homo sapiens, ie. you and me. At various points along this long and arduous journey certain important milestones were reached, and one of the most significant was the time when archaic humans began walking on two legs rather than four, making them (us) upright-walking bipeds. Because this adaptation was so important, evolutionary scientists have been striving for decades to discover exactly when this vital change took place. This has not been an easy challenge, since well-preserved fossils of ancient humans and related species are so difficult to find. But a new analysis just published in the journal Nature contends that the switch from quadrupedal to

