The genus Homo is thought to have emerged about 2 to 2.5 million years ago, but it seems our early hominin ancestors were already walking fully upright by then.
Fossil footprints that date back to 3.6 million years ago, and which have now become the "earliest direct evidence of hominin bipedalism," revealed that our early ancestors evolved the hallmark upright walk that we use today, with a vertical torso and extended legs, substantially earlier than previously believed, Phys.org reports.
The conclusion comes from evolutionary anthropologist David Raichlen of the University of Arizona, who presented his research at a symposium on the evolution of human locomotion, held yesterday (April 22) during the 2018 Experimental Biology Conference in San Diego.
"Upright, humanlike bipedal walking goes back 4 to 5 million years," Raichlen told the Washington Post prior to the symposium.
Hominins are thought to have begun walking on two legs around 7 million years ago, but the early walking mechanics were characterized by a crouched posture, with bent knees and hips, described by Raichlen as flexed limb mechanics. This is quite similar to the way chimpanzees walk, notes the Washington Post.
"By 3.6 million years ago, our data suggest that if you can account for differences in size, hominins were walking in a way that is very similar to living humans," Raichlen explained in a statement.