Earliest Humanlike Footprints Found In Kenya

A 1.5 million-year-old fossil footprint found near Ileret, Kenya. i i

hide captionThis fossil footprint found near Ileret, Kenya, is 1.5 million years old. These footprints are the oldest ever found of the human genus.

Matthew Bennett/Bournemouth University
A 1.5 million-year-old fossil footprint found near Ileret, Kenya.

This fossil footprint found near Ileret, Kenya, is 1.5 million years old. These footprints are the oldest ever found of the human genus.

Matthew Bennett/Bournemouth University
A trail of fossil footprints found in Kenya show all the hallmarks of a modern human stride. i i

hide captionLaser scanning of the footprints show all the hallmarks of a modern human stride.

Matthew Bennett/Bournemouth University
A trail of fossil footprints found in Kenya show all the hallmarks of a modern human stride.

Laser scanning of the footprints show all the hallmarks of a modern human stride.

Matthew Bennett/Bournemouth University
The  footprints may have been made by Homo ergaster/erectus based on estimates of  height and weight i i

hide captionThe footprints were probably made by Homo erectus, and they match a men's shoe size of about 9. This one looks very much like the footprint of anthropologist Brian Richmond.

Brian Richmond
The  footprints may have been made by Homo ergaster/erectus based on estimates of  height and weight

The footprints were probably made by Homo erectus, and they match a men's shoe size of about 9. This one looks very much like the footprint of anthropologist Brian Richmond.

Brian Richmond

Scientists digging in a Kenyan desert have found what they believe to be the oldest humanlike footprints. Several individuals laid them down 1.5 million years ago in what was a muddy track.

The scientists discovered not just one set of footprints, but two. The second set was left about 1,000 years after the first set. "It's incredible. I've never excavated anything like this before," says team director John Harris of Rutgers University.

Reporting in this week's issue of the journal Science, the anthropologists say the creatures that made the prints were probably Homo erectus. That's believed to be a direct ancestor of modern humans, and one that appears to have been built much the way modern humans are.

"The prints match a men's shoe size of about 9, which gives you a height of about 5 feet 9 inches," says Brian Richmond of George Washington University, who was part of the excavation team. "Here, we have really compelling evidence that they were walking with a long stride, they had an arch in the foot the way we have, and the arch puts a spring in our step, which makes walking more efficient," he says.

The region is rich with animal footprints as well, including antelopes, a form of zebra and birds. During the time the prints were made, the region was probably a river valley near a lake.

The evolution of an arch in the foot indicates a spring ligament in the foot, which increases the efficiency of walking by storing some of the energy from the falling weight of the walker in each step, and then returning it up the leg on the rebound. The big toe is also aligned with the other toes, something not found in earlier ancestors and other primates. Its large size is necessary to absorb the walker's weight as the foot rolls forward and then lifts off the ground before the next step.

Harris says the area where these individuals lived was undergoing a drying period at the time the prints were made. Trees and water might have been growing scarce, so Homo erectus would have had to walk farther for water and food.

Dan Lieberman, an anthropologist at Harvard University, says the footprints confirm that the evolution of the foot was crucial to becoming human. For one thing, it allowed people to run.

"Imagine you are a Homo erectus and you are hungry," he says. "And you want to kill something for dinner. The weapons available to you are incredibly primitive, so one thing early hominids might have included in their repertoire of hunting strategies was to run animals in the heat."

Eventually, he says, the prey would collapse and could then be killed.

The scientific team will return to the site next summer. They say the first track ends at a small hill, and they expect to find more prints underneath the hill.

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