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Foot fossils reveal new pre-human species

JOHNS HOPKINS (US) — The discovery of fossilized bones reveals the existence of a previously unknown species of pre-human, and may shed light on how humans began walking upright.

The partial foot was discovered in an area of eastern Africa that was also home to Australopithecus afarensis, the species known for the famous fossilized skeleton nicknamed “Lucy.”

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The recently discovered foot skeleton has characteristics (such as an opposable big toe bone) that don’t match those of Lucy. It provides the first evidence that at least two species of pre-human ancestors lived between 3 million and 4 million years ago in the Afar region of what is now Ethiopia.

“The foot belonged to a hominin species—not yet named—that overlaps in age with Lucy,” says Johns Hopkins University geologist Naomi Levin. “Although it was found in a neighboring project area that is relatively close to the Lucy fossil site, it does not look like an A. afarensis foot.”

Levin, an assistant professor of earth and planetary sciences, is part of a team led by Yohannes Haile-Selassie of the Cleveland Museum of Natural History. Researchers from Case Western Reserve University and the Berkeley Geochronology Center were also on the team.

They reported their discovery in the March 29 issue of Nature. The right foot fossil, dated to approximately 3.4 million years ago, was discovered in 2009 in sediments in the Burtele area of Afar, about 325 miles northeast of Addis Ababa.

Lucy, the A. afarensis individual whose partial skeleton was discovered in 1974 about 30 miles south of Burtele, is believed to have died just under 3.2 million years ago.

Lucy’s newly found ‘neighbors’ in Afar might have spent at least some of their time up in the trees.

“What is clear,” Levin says, “is that the foot of the Burtele hominin was able to grasp items much better than its contemporary, A. afarensis, would have been able to do, which suggests that it was adept at moving around in trees.”

That is important, she says, because it shows that there is much more to learn about the role of locomotion in human evolution. The discovery could shed light on how our ancestors learned to walk upright.

“This fossil makes the story of locomotion more complex, and it shows that we have a lot more to learn about how humans transitioned from moving around in trees to moving around on the ground on two legs,” Levin says. “This fossil shows that some hominins may have been capable of doing both.”

The Afar region is now very hot and dry. The researchers, citing geological findings and the range of fossil animals found near the site, believe the area was wetter and more wooded when the Burtele hominin lived.

“We’re just at the beginning of understanding the environmental context for this important fossil,” Levin says. “It will be a critical part of understanding this hominin, its habitat and the role that the environment played in its evolution,” she says.

More news from Johns Hopkins: http://releases.jhu.edu

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