A remarkable set of human footprints from 1.5 million years ago has been discovered in Africa, suggesting that the human feet of ancient times walked much as we do today.

Three tracks found near Ileret in northern Kenya have been identified as the second oldest made by prehistoric human relatives and the oldest prints left by feet with a recognisably modern anatomy.

The find casts important new light on the evolution of humanity’s upright stride, suggesting that Homo erectus, an ancestral species that emerged about 1.8 million years ago, walked with an upright gait little different from our own.

Homo erectus is thought to have been the first species of ancient humans to migrate out of Africa and its efficient, two-legged biomechanical style may have been critical to this, scientists said.

The Ileret discovery is the first of ancient human footprints since the famous Laetoli tracks, from 3.75 million years ago, were discovered in Tanzania in 1978 by a team led by Mary Leakey.

While the Laetoli tracks confirmed that some ancestral humans, or hominins, could walk upright on two legs, the Ileret footprints are the earliest that reveal an anatomy and stride that is unambiguously adapted for a bipedal gait.

Australopithecus afarensis, the primitive human relative that walked at Laetoli, had a splayed big toe similar to that of apes and scientists disagree whether it was exclusively bipedal or sometimes walked on its knuckles like modern chimpanzees.

By contrast, the Ileret prints, which were probably made either by Homo erectus or a subspecies called Homo ergaster, reveal an anatomy almost indistinguishable from that of Homo sapiens.

They show a big toe parallel to the other toes, a large and robust heel, a high arch and short toes, all of which are characteristic of modern humans. This points towards an upright gait that we would recognise as very similar to our own.

Matthew Bennett, of Bournemouth University, who led the study team, said the find was particularly important because no Homo erectus foot bones survive in the fossil record.

“Carnivores are partial to hands and feet, so nothing was preserved,” he said. “We knew its anatomy was adapted for bipedalism, but we knew nothing about a critical element of its biomechanics: its feet.

“Now we know that 1.5 million years ago, Homo erectus had feet with an anatomy very similar to modern humans. It could essentially walk with the same biomechanical efficiency as you or I.”

He added that the species’s bipedal locomotion could have made it possible for Homo erectus to migrate beyond Africa. “It was adapted for long-distance walking,” he said.

The ancient footprints, details of which are published in the journal Science, were found in two different layers of sediment. The upper one includes two trails of two prints, one trail of seven prints, and several isolated prints, while the lower layer has preserved one trail of two prints and another single print, probably left by a juvenile.

All the prints have been reliably dated to between 1.51m and 1.53m years ago from the age of the volcanic ash embedded in the rocks in which they were found.

Professor Bennett’s team has scanned the prints using a laser technique to create detailed models that allow them to be studied without damaging them. These scans have exposed the remarkably modern anatomy of the feet that made the prints.

Brian Richmond, of George Washington University in Washington, DC, a member of the study team, said: “The discovery of hominin [ancestral human] footprints is an incredibly rare event and the new prints are the second oldest in the world after the Laetoli prints in northern Tanzania, making this one of the most important discoveries in recent years with respect to research on the evolution of human gait.

“The size and stature estimates derived from the Ileret prints compare well with those of Homo erectus and are too large to have been formed by other hominin species living in this part of Africa in the early Pleistocene.”

John Harris, of Rutgers University, another team member, said: “These footprints, together with evidence from the archaeological record, support the hypothesis of a hominin with a larger home range and enhanced dietary quality, giving us an emerging picture of the paleobiology of early Homo erectus that suggests a shift in cultural and biological adaptations relative to earlier hominins.”

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