Vestige of upright stride is at least 1.5m years old

African fossil like modern footprint

Ancient footprints in Kenya were left by individuals thought to have been about 5 feet, 9 inches tall. (AFP/Getty Images)

WASHINGTON - Footprints found in Kenya that resemble those left in wet sand by beachgoers today show that 1.5 million years ago, a human ancestor walked as we do, with anatomically modern feet, scientists said yesterday.

The remains of the footprints found in sedimentary rock near Ileret in northern Kenya most likely were left by a human ancestor called Homo erectus, also known as Homo ergaster, an international team of scientists wrote in the journal Science.

The scientists found a series of footprints, including one apparently by a child, left by individuals walking on a muddy river bank. Judging from stride length, they estimated the individuals were about 5 feet, 9 inches in height.

"It was kind of creepy excavating these things to see all of a sudden something that looks so dramatically like something that you yourself could have made 20 minutes earlier in some kind of wet sediment just next to the site," said archeologist David Braun of the University of Cape Town in South Africa. The footprints show that the individuals had a big toe parallel to the other toes, unlike that of apes, for which it is separated in a grasping configuration useful in trees. The footprints show a characteristic human-like arch and short toes, typically associated with an upright, bipedal stance.

The size, spacing, and depth of the impressions allowed the scientists to estimate weight, stride, and gait, which all were found to be within the range of modern humans.

Homo sapiens first appeared 200,000 years ago. But the finding shows that as far back as 1.5 million years ago, the human lineage walked with a modern stride, the researchers said.

These are the second-oldest known footprints of human ancestors. The oldest, found in Tanzania, date from about 3.75 million years ago and apparently were made by a much more primitive human ancestor.