More than a million years ago an ancient human ancestor walked across a sandy plain in eastern Africa, leaving footprints that scientists are now hailing as the earliest evidence of modern upright walking.
The footprints, dated to between 1.51 million and 1.53 million years ago, were discovered at Ileret, Kenya, researchers report in Friday's edition of the journal Science.
With a large toe parallel to the other toes, the prints indicate a modern upright stride, the researchers said. They are likely to have been made by the early hominid Homo ergaster or early Homo erectus.
Older footprints, dating to 3.6 million years ago found in Tanzania have been attributed to the less advanced Australopithecus afarensis. Those prints indicate an upright posture but with a shallower arch and a more ape-like, divergent big toe.
"These footprints are one of the most important discoveries of recent years, and the museum is doing everything possible to ensure the safety of this unique site," Emma Mbua of the National Museums of Kenya, said in a statement.
The lead researcher was Matthew R. Bennett of Bournemouth University in Britain. Others taking part included John W. K. Harris of Rutgers University and Brian G. Richmond of The George Washington University and the Smithsonian's National Museum of Natural History.