PHOENIX, Feb. 10 (UPI) -- U.S. researchers say fossil evidence suggests a key human ancestor could walk upright consistently, a major advance in human evolution.
A 3.2-million-year-old foot bone found at Hadar, Ethiopia, indicates the diminutive, human-like species Australopithecus afarensis had arches in its feet, suggesting upright locomotion, the BBC reported Thursday.
Arched feet, the researchers say, are critical for walking the way modern humans do.
"[The bone] gives a glimpse of foot anatomy and function," says William Kimbel, director of the Institute of Human Origins at Arizona State University.
"The bone that was recovered from the Hadar site has all the hallmarks of the form and function of the modern human foot."
Paleontologists knew A. afarensis spent some of its time standing up from examination of the first discovered skeleton of the species, dubbed "Lucy," also found near Hadar in the Ethiopian rift valley.
But the absence of important foot bones in all the specimens found so far made it difficult for researchers to determine exactly how much time Lucy and her kin spent on their feet, as opposed to moving through the branches of trees.
Other features of the skeletons, like the spine and leg bones, suggested upright walking.
"Now we can say that the foot, too, joins these other anatomical regions in pointing towards a fundamentally human-like form of locomotion in this ancient human ancestor," Kimbel says.
