When did our ancestors begin walking on two legs? This evolutionary question about our terrestrial bipedalism has piqued paleoanthropologists for years.
But this latest study looks at the strength of bone shafts of each species, which reflects the physical demands placed on them and how much time each species spent on trees, rather than just at the skeletal shape of their limbs. The bone strength ratios of arms and legs bone in these fossils was compared to those of modern humans, chimpanzees, gorillas and orangutans. Now, a new study gives us the most conclusive evidence of when archaic humans transitioned from regularly climbing trees to habitually walking upright on the ground: and the answer is 1.8 million years ago. Scientists from the University of the Witwatersrand (South Africa) and University of Southern California arrived at this conclusion after studying the internal strength of limb bones from two fossil skeletons: one, the Little Foot (a 3.67-million-year-old Australopithecus individual from Sterkfontein Cave in South Africa) and a 1.8-million-year-old archaic human from Georgia. Much research has focused on determining the when this locomotor behaviour changed in human evolution, going back to our common ancestor, that is the time when human and chimpanzee lineages diverged 9.3 to 6.5 million years ago. In 2020, another research paper published in the Proceedings of the National Academy of Sciences , which studied the shape and structure of fossil leg bones suggested that our human ancestors could have been regularly climbing trees two million years ago.
“Since the time of Darwin and Huxley, terrestrial bipedalism has been posed as a central tenet of the human ecological niche,” said the research paper published in the journal Science Advances .
