Bipedalism

Bipedalism is an important aspect of modern humans and our last ancestors. It's origin however, is highly debated. Some attribute it to the group of hominids known as Australopithecus, whose skeletal remains match up with the correct requirements for upright walking such as the curvature of the spine and correct shape of the pelvis. Another interesting aspect about Australopithecus and their skeletal structure is that their arms allowed them to be both partially arboreal and partly terrestrial with their spines and pelvises. This means it falls near the evolutionary split between small bodied arboreal primates and the large bodied terrestrial hominins like us. However, there is so much variety between species in the group Australopithecus that it's hard to determine what species exactly survived long enough and passed their traits onto us (like bipedality) or which ones eventually went extinct and did not.