Fossil footprints left 1.5 million years ago in Africa by the ancestors of modern humans show their feet and gait weren't much different from ours.
The three footprint trails uncovered in northern Kenya over the last three years are the oldest evidence discovered so far of human-like feet without ape-like features such as a splayed big toe for grasping branches, said a paper published in Friday's issue of Science.
They indicate that the human ancestors who left the prints, believed to be members of the species Homo ergaster or Homo erectus based on their estimated size, touched the ground first with their heels and then transferred their weight to the balls of their feet and then their big toes as they walked.
The feet themselves had a high, human-like arch with short toes.
The footprints were excavated between 2006 and 2008 near Ileret, Kenya, by students at Koobi Fora Field School, which is operated by Rutgers University in New Jersey and the National Museums of Kenya.
They were in a layer of fine sand sandwiched between layers of volcanic ash. The age of the ash indicated the footprints were about 1.51 million to 1.53 million years old.
An international team led by professor Matthew Bennett of Bournemouth University in the United Kingdom analyzed the prints using laser scanning.
The prints showed significant differences from 3.6 million-year-old fossil footprints discovered in 1978 by archeologist and anthropologist Mary Leakey in Laetoli, Tanzania. Those showed a shallower arch and splayed big toe more similar to prints made by apes and were attributed to an earlier, more ape-like human ancestor called Australopithecus afarensis.