1.8 Million-Year-Old Hominid Jaw Found

John Roach
for National Geographic News
February 20, 2003
Tanzania's Olduvai Gorge has yielded an impressive pile of fossilized bones and stone tools that may reshuffle the evolutionary tree of the early hominids and shed light on the behavior of some of human kind's earliest ancestors.

The gorge is most noted for the abundant fossil discoveries of esteemed anthropologists Louis and Mary Leakey from 1959 to 1976 which helped shape modern understanding of human origins.

The new find reported by Robert Blumenschine, an anthropologist at Rutgers University in New Brunswick, New Jersey, and an international team of colleagues includes an exquisitely-preserved 1.8 million-year-old fossilized hominid upper jaw, hundreds of stone tools, and butchered animal bones.

Blumenschine and colleagues describe the find in the February 21 issue of the journal Science.

The jaw bone is intact with all its upper teeth and the lower face, giving the scientists a unique opportunity to advance theories on the evolution of early humans.

"These things are so darn rare," said Blumenschine. "For early genus Homo there are maybe 50 specimens known. This one is complete enough to be ranked in the top ten, if not top five, of fossils of earliest genus Homo."

The scientists assign the fossil, simply known as Olduvai Hominid (OH) 65, to Homo habilis, the earliest member of the genus Homo, the genus of humans. H. habilis was the first hominid to display traits such as tool technology, larger brain size, and a taste for large animals.

"These are all unusual traits and fundamental to what modern humans are all about," said Blumenschine.

Reshuffled Deck?

The hominid fossil provides what Blumenschine calls an anatomical link between the two earliest members of the genus Homo, H. habilis, and H. rudolfensis, thus providing evidence that H. rudolfensis is not a separate species as some anthropologists claim.

The link is between a cranium known as ER 1470 found by Richard Leakey in northern Kenya in 1972 and described as H. rudolfensis and the original H. habilis specimen OH 7, a mandible or lower jaw, Mary and Louis Leakey's team found in 1960 at Olduvai Gorge.

"What we are arguing is that the ER 1470 cranium would fit nicely on the OH 7 mandible, and OH 65 provides the anatomical link," said Blumenschine. "We are suggesting that H. rudolfensis is not a valid taxonomic name, just a junior synonym of Homo habilis."

Ian Tattersall, curator in the department of anthropology at American Museum of Natural History in New York, New York, said he is confident the authors made a solid observation about the match between ER 1470 and H. habilis but it is not proof.

"Too bad that the Homo habilis type is a mandible and this is a maxilla [upper jaw], because if OH 7 and ER 1470 are the same thing, then habilis and rudolfensis would indeed be synonyms," he said.

Blumenschine and his colleagues also suggest that several other fossils currently assigned to H. habilis are misfits because of smaller brain sizes and other details and should therefore be renamed. "What we are arguing is a reshuffling of specimens," said Blumenschine.

Tattersall says claims that a new fossil find will cause a reshuffling of the deck are "de riguer" among those who make a living out of digging up old artifacts and bones but are not prudent.

"When Leaky was working at Olduvai in 1960 and thereabouts, it may have been possible to make such a claim. But the hominid fossil record is now so big that it is unlikely that any one fossil will totally revolutionize interpretation," he said.

Tools and Butchered Bones

Blumenschine and colleagues were in Tanzania as part of a multi-year, multi-disciplinary program to figure out the adaptive strategies the early hominids evolved in order to survive over the entire area of the Olduvai Lake Basin.

Earlier research suggested that the hominids spent most of their time on the eastern side of the lake, which lay closer to the volcanic highlands, a major source of freshwater.

Blumenschine and Charles Peter, a co-author of the paper and researcher at the University of Georgia in Athens, hypothesized that the hominids might occasionally migrate to the lake basin's drier western side during wetter periods.

The research team was excavating trenches on the western side of the gorge when they unexpectedly found the hominid fossil in 1995 along with stone tools and bones from larger animals that have marks made by stone knives and hammers.

"Most of the stone tools were made from material that can be found locally near the western gorge, but a few tools were made of material derived from the volcanic highlands to the east," said Blumenschine.

This is evidence, he said, that the hominids carried some of their tools with them as they trekked 12 to 16 miles (20 to 25 kilometers) around the lake, which fits in with the researchers' general models of how the early hominids used the lake.

"Such a migratory, resource- and shelter-based pattern indicates behavioral flexibility and an adaptable lifestyle of these early Homo people," said Phillip Tobias, a paleoanthropologist at the University of Witwatersrand in Johannesburg, South Africa, in an accompanying perspective in Science.

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Additional National Geographic Resources
Interactive Feature: Outpost: In Search of Human Origins
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