NEW BRUNSWICK/PISCATAWAY, N.J. - The fossilized jaw of a 1.8 million-year-old human ancestor (hominid) from Tanzania may just be one of the five best specimens out of about 50 known to represent the earliest members of the genus Homo (H) – the genus to which the human species belongs.
In the Feb. 21 issue of the journal Science, Rutgers anthropology Professor Robert Blumenschine and his colleagues describe and discuss the specimen they found at Olduvai Gorge in 1995, a fossil-rich locale that gained prominence through the discoveries of Louis and Mary Leakey in the early 1960s.
"This is an important ancestor that comes from a crucial time range in prehistory – a time when we first began to see stone tools, when hominids had just begun to exploit larger animals as a food source, and when brain size was just beginning to expand significantly," said Blumenschine.
The newly described fossil, designated OH 65, consists of a maxilla (upper jaw) complete with all its teeth and the lower face. "Any time you make a find like this, complete enough to show so many important diagnostic features, we get very excited," he said.
The Science article reports that the fossil provides a key anatomical link between two other known specimens, H. rudolfensis - a cranium with most of its face (but no teeth) from northern Kenya - and the original H. habilis type specimen - a mandible (lower jaw) found previously at Olduvai. "OH 65 allows us to reshuffle the specimens that belong in the ancestral genus and tie together rudolfensis and habilis," said Blumenschine. "It shows that all three specimens are likely to be members of the same species - Homo habilis."
OH 65 was found with stone tools and with bones from larger animals that clearly show cut marks made by stone knives and hammer-stone impact marks. Blumenschine said that this associated evidence further corroborates the work of other scientists in demonstrating the capacity both to make tools and to use them in butchering meat for food, even at this early time horizon. Geological evidence in combination with the animal remains offered the investigators an opportunity to develop additional information about early man's land use and his relationship with his environment.
"As we learn more about the paleoecology, we may begin to understand what environmental conditions were selecting for adaptive traits in early Homo, traits like an increasingly large brain, that eventually gave rise to what we are today," said Blumenschine.
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