Anthropologists have uncovered ancient fossil footprints in Kenya dating back 1.5 million years, the oldest evidence yet that our ancestors walked like present-day humans, a study showed Thursday.
The footprints were discovered in two sedimentary layers near Ileret in northern Kenya and revealed an essentially modern human-like foot anatomy.
The impressions came from the Homo ergaster, or early Homo erectus, the first hominid whose longer legs and shorter arms corresponded to the body proportions of the modern Homo sapiens, the study's authors said.
The footprints provided information on the soft tissue form and structure that are not usually available in fossilised bones, explained Matthew Bennett of Bournemouth University in Britain, the lead author of the study published in the journal, Science.
Bennett scanned and digitized the footprint to make sure that comparisons with modern human and other fossil hominid footprints were objective.
The upper sediment layer contained three footprint trails: two trails of two prints each, a trail of seven prints and several isolated prints.
The other sediment layer, five meters (16 feet) deeper, preserved a trail of two prints and a smaller isolated print that the authors said probably was that of a child.
In all specimens, the big toe was parallel to the other toes, unlike apes, whose big toes are separated to help grasping tree branches. The Ileret footprints also show a pronounced arch and short toes that are human-like and are usually associated with the ability to walk on two feet.
Several Homo ergaster and Homo erectus fossils dating from the same era as the Ileret prints have been found in Tanzania, Ethiopia, Kenya and South Africa.
In 1978, British archeologist and anthropologist Mary Leakey discovered footprints in Laetoli, Tanzania that dated back 3.6 million years. But those prints were attributed to a less advanced creature, the Australopithecus afarensis, that showed a shallower arch and a more ape-like separated big toe.