Analysis: A close look at chimpanzees challenges old theories on why humans walk on two legs

Dr Alexander Piel and Dr Fiona Stewart (both UCL Anthropology) discuss their new study in The Conversation which reveals the ability for humans to walk upright on two legs may have evolved in trees, and not on the ground as previously thought. There's no trait that distinguishes humans from all other mammals more clearly than the way we walk. Human habitual bipedalism - obligatory walking on two legs - has long been a defining trait of our species, as well as our ancestors as far back as 4.5 million years ago. Science's growing understanding of chimpanzee culture, communication and emotion may have blurred the understanding of "distinctly human", but our obligatory bipedalism has stood the test of time. Why, when, and where bipedalism evolved remains debated, however. Numerous evolutionary pressures have been proposed. Most are about the economics and energy use of walking on two legs (bipedalism is far more efficient than quadrupedalism).