The earliest direct ancestors of modern humans may have looked more like apes than previously thought, a new study suggests.
But the findings, based on a reconstructed 1.9-million-year-old skull, are highly controversial among the anthropological community.
New computer-generated reconstructions suggest that the specimen had a smaller brain than scientists had believed as well as a distinctly protruding jaw.
"We see in this new reconstruction primitive features that are carryovers from what may be its Australopithecus ancestor," said study author Timothy Bromage, an adjunct professor at New York University College of Dentistry.
Australopithecus is an extinct apelike creature closely related to humans that lived up to four million years ago (see photos of fossils belonging to the oldest known Australopithecus child).
But other experts expressed skepticism about Bromage's argument that the repositioning of the specimen's face means its brain size must have been smaller.
"It's probably right that the face should stick far more forward. But to say that because they've changed the angle of the face, the brain size has to get smaller doesn't make any sense," said Robert Martin, a biological anthropologist at the Field Museum in Chicago, Illinois.
"The [specimen's brain] certainly isn't as small as [Bromage is] now arguing."
Bromage presented his study at the recent annual meeting of the International Association for Dental Research in New Orleans, Louisiana.
Half-Size Brain?
The skull used for the reconstruction was found in 1972 by Bernard Ngeneo, a member of a team led by anthropologist Richard Leakey, at Lake Turkana in Kenya's Great Rift valley.
Named KNM-ER 1470, the fossil skull has been at the center of much debate concerning its species.
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