Lucy did not walk alone, fossil indicates

  • Updated: March 31, 2012 - 5:12 PM

The ancient human relative may have shared eastern Africa with another hominin, but one that spent much of its time in the trees. Summary.

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This image provided by the Cleveland Museum of Natural History shows a bone fragment from a 3.4-million-year-old partial foot recovered during an excavation in Ethiopia. A new study determined that the foot belonged to a human relative that lived around the same time as Lucy, the famous early hominid. (AP Photo/Celeveland Museum of Natural History, Yohannes Haile-Selassie) � �

Photo: Yohannes Haile-Selassie, Associated Press - Ap

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Lucy, that starlet among ancient human relatives, may have shared the stage with a hominin very different from herself, a newly discovered fossil suggests.

Out of the Ethiopian desert, researchers have unearthed a rare, 3.4-million-year-old partial foot that resembles those belonging to Ardipithecus ramidus, a species thought to have roamed East Africa a million years before Lucy and other members of her species, Australopithecus afarensis. The findings, published in the journal Nature, provide the first good evidence that another bipedal human relative was still climbing trees at the same time that Lucy and her kind had their feet planted on the ground.

Foot bones are seldom found intact because they're usually too delicate to survive in harsh environments, said Bruce Latimer, a paleoanthropologist at Case Western Reserve University in Cleveland. This makes the new fossil, made up of eight bones from the front part of a right foot, a valuable find -- particularly since it has several toes intact, allowing scientists to get a better sense of how the foot operated.

Lucy's foot shares many fundamental qualities with those of modern humans. Our big toes are large and parallel with the other four, and all are able to bend and push off the ground, making Homo sapiens an excellent walker.

This new fossil, however, has more apelike features and closely resembles that of A. ramidus, whose most famous member is the specimen known as Ardi. These creatures had some adaptations for walking on the ground, but they also sported a foot with a grasping big toe that wasn't very convenient for walking but was excellent for climbing trees. On the ground, Ardi would have shifted her weight to her outside toes, making for an awkward gait in comparison with Lucy.

Perhaps most surprisingly, the metatarsal bone of the fourth toe was longer than in the first toe -- a feature that hadn't been observed in Ardi before.

"When I first saw this, I was shocked by it," Latimer said. Though other hominin species are known to have coexisted at other times, the discovery reveals an unexpected diversity among hominins during Lucy's time, about 3 million years before anatomically modern humans first emerged.

LOS ANGELES TIMES

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