Why humans walk on two legs: a close look at chimpanzees puts some old theories to the test

Issa chimpanzees live in a woodland dominated environment interspersed with riparian forests, grasslands, and rocky out-crops. Photo: R. Drummond-Clarke/GMERC

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.