What Made Our Species Unique: Walking The Laetoli footprints discovered in northern Tanzania offer some 3.66-million-year-old evidence of our walking ancestors.Credit...Images of Africa Photobank/Alamy Stock Photo Buy Book ▾ By Rebecca Wragg Sykes FIRST STEPS By Jeremy DeSilva Walking: We marvel when other animals get up on their hind legs and do it, applaud our children when they master it, but most of the time blithely ignore how remarkable a feat it really is. Yet moving bipedally (on two legs) has proved fiendishly tricky to explain from an evolutionary perspective. Enter “First Steps,” by the paleoanthropologist Jeremy DeSilva, a book that strides confidently across this complex terrain, laying out what we know about how walking works, who started doing it and when.