NAIROBI, Kenya, Feb. 27, 2009  -- Scientists have discovered footprints in northern Kenya that prove human beings have been walking our walk for at least 1.5 million years.

The footprints belonged to a Homo ergaster, one of the earliest ancestors of modern humans, believed to have lived throughout southern and eastern Africa. Scientists have been digging in northern Kenya, near the Turkana basin, looking for fossils and other clues to how human beings evolved.

Matthew Bennett, a professor of environmental and geographical sciences at Bournemouth University in the United Kingdom, was the lead scientist on the excavation team. The discovery of the footprints is an exciting breakthrough, he said.

"It's filling in a real gap in our knowledge about when people developed a modern foot anatomy," Bennett told ABC News. "It brings back the age of when essentially a modern footprint was in operation."

The footprints themselves have all the characteristics of human feet today: short toes, a big toe parallel to the others and a high arch. The prints also indicated that the Homo ergaster walk was similar to the human walk of today, with weight being transferred from the heel of the foot to the ball and then to the big toe.

After uncovering the prints in separate rock layers near the village of Ileret, Bennett and his team scanned the prints to compare them to the last discovery of footprints 30 years ago. Those prints were found at the Laetoli site in Tanzania and belonged to the Australopithecus, a more primitive human ancestor from 3.5 million years ago that exhibited characteristics closer to apes than modern-day humans.

Comparing the new prints with both the Laetoli footprints and the footprints of today, the team of scientists concluded in an article in the journal Science that "The Ileret prints show that by 1.5 million years, hominids had evolved an essentially modern human foot function and style of bipedal locomotion."

Bennett said that the excavation process and results are about more than just science. Knowing that the last time someone was at the site was more than 1 million years ago "provides a very strong emotional linkage to our former ancestors," he said. "It's a slow process, but it's a very emotional process."

Understanding Past and Future

To preserve the site for future excavations, the prints have been reburied and will not be uncovered until the next dig scheduled for this summer. The project is an international collaborative effort, drawing scientists and students from all over the world. Bennett and his team are working with the Kenya National Museum to ensure that the area continues to be a place where scientists can dig for discoveries that show just how universal the human species is.

"It helps us understand our past," he said. "And it helps us understand our future too."