The question of whether our early ancestors walked fully upright or in a crouched position, like apes, has long been a hot debate among scientists.
Now, new research presented at the annual meeting of the American Association of Anatomists during the 2018 Experimental Biology Conference in San Diego suggests that the characteristic bipedalism of modern humans may have evolved much earlier than previously thought—long before our species had even emerged.
For the research, evolutionary anthropologist David Raichlen and his colleagues from the University of Arizona, examined 3.6-million-year-old hominin footprints recently discovered in Laetoli, Tanzania, which represent the earliest direct evidence of hominin bipedalism.
When analyzing footprints, looking at the difference between the impressions made by the toe and the heel reveals how the center of pressure moves along the foot during a step and therefore provides clues to walking posture. After comparing the footprints, the results showed that the Laetoli prints were much more similar to those made by humans walking upright.
Walking in this manner with fully extended legs is more efficient—and therefore uses less energy—than shuffling in a crouched position. This means longer journeys can be undertaken, suggesting that the evolutionary switch from one mode of walking to another may have been linked to how human ancestors looked for food, according to the researchers.