Prints show modern foot in prehumans

John Noble Wilford
New York Times News Service
28 February 2009
Waterloo Region Record

Footprints uncovered in Kenya show that as early as 1.5 million years ago an ancestral species, almost certainly Homo erectus, had already evolved the feet and walking gait of modern humans.

An international team of scientists, in a report yesterday in the journal Science, said the well-defined prints in an eroding bluff east of Lake Turkana "provided the oldest evidence of an essentially modern humanlike foot anatomy." They said the find also added to evidence that painted a picture of Homo erectus as the prehumans who took long evolutionary strides -- figuratively and, now it seems, also literally.

Where the individuals who made the tracks were going, or why, is beyond knowing by the cleverest scientist. The variability of the separation between some steps, researchers said, suggests that they were picking their way over an uneven surface, muddy enough to leave a mark -- an unintended message from an extinct species for the contemplation of its descendants.

Until now, no footprint trails had ever been associated with early members of our long-legged genus Homo. Preserved ancient footprints of any kind are rare. The only earlier prints of a protohuman species were found in 1978 at Laetoli, in Tanzania.

Dated at 3.7 million years ago, they were made by Australopithecus afarensis, the diminutive species to which the famous Lucy skeleton belonged. The prints showed that the species already walked upright, but its short legs and long arms and its feet were in many ways apelike.

Studying the more than a dozen prints, scientists determined that the individuals had heels, insteps and toes almost identical to those in humans, and that they walked with a long stride similar to human locomotion. The researchers who made the discovery, as well as independent specialists in human origins, said the prints helped explain fossil and archeological evidence that erectus had adapted the ability for long-distance walking and running. Erectus skeletons from East Asia revealed that the species, or a branch of it, had migrated out of Africa as early as 1.8 million years ago.

The lead author of the journal report, Matthew R. Bennett, a dean at Bournemouth University in England, analyzed the prints with a new laser technology for digitizing their precise depths and contours. The tracks were excavated over the last three years by paleontologists and students directed by John W.K. Harris of Rutgers University in collaboration with the National Museums of Kenya.

Daniel E. Lieberman, a professor of biological anthropology at Harvard who studies the evolution of human locomotion but was not a member of the research group, said the prints established what experts had suspected for some time. Erectus, he said, "probably looked much like us, both walking and running over long distances."

One obvious exception: the erectus brain, which was more advanced than those of previous ancestors, but was still much smaller than the Homo sapiens brain.

The site of the discovery is about eight kilometres east of Lake Turkana, near the village of Ileret, in northern Kenya.

Harris of Rutgers said that excavations from 2005 through last year yielded scores of animal tracks as well as the erectus footprints.