We are the only primates walking exclusively on two legs. Doing so leaves our hands free to make and use tools.
This, the experts claim, was a crucial development in the evolution of early humans. But there is little consensus as to how the radical change from walking on all fours to standing upright came about. In a paper recently published, Kansas-based physicists Adrian Melot and Brian Thomas put forward a novel theory. Supernovae, they claim, forced our ancestors to become bipeds. Read more.