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 The fossils shed new light on a key period in the human lineage's
evolution before the emergence of our genus Homo and provide the
first evidence that two early human ancestor species lived at the
same time and place prior to 3 million years ago, they said in
announcing the discovery on Wednesday.
The new species, Australopithecus deyiremeda, combined ape-like and
human-like traits as did Lucy's species, Australopithecus afarensis,
but was sufficiently different to warrant recognition as a separate
species, they said.
Lucy's skeleton was unearthed in 1974 about 30 miles (50 km) from
the new fossils' location.
The new species' cheekbone position and generally small tooth size
likely made it look more like our genus than did Lucy's species,
said Cleveland Museum of Natural History paleoanthropologist
Yohannes Haile-Selassie, who led the study published in the journal
Nature.
The scientists found upper and lower jaws and teeth from at least
three individuals, but no other remains. They previously found a 3.4
million-year-old partial fossil foot and "cannot rule out" that it
belongs to the new species, Haile-Selassie said.
Compared to Lucy, the new species had a more robust lower jaw, cheek
bones further forward on the upper jaw, molars with thicker enamel
and relatively small upper and lower cheek teeth, said
paleoanthropologist Stephanie Melillo of the Max Planck Institute
for Evolutionary Anthropology's Department of Human Evolution in
Germany.
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One unanswered question is how Lucy's species and the new one
managed to co-exist.
"They would have been rivals if they were exploiting the same
resources or had similar foraging strategies," Haile-Selassie said.
Dental differences suggest they had different diets, meaning they
may not have competed for the same resources. Another human
relative, Kenyanthropus platyops, also lived relatively nearby in
Kenya.
Our species, Homo sapiens, appeared 200,000 years ago. The earliest
known member of our genus lived 2.8 million years ago. Scientists
previously had argued there was only one human ancestor at any time
between 4 and 3 million years ago, each giving rise to another new
species.
"The story is becoming more complicated as more branches are added
to the human phylogenetic tree," Melillo said.
(Reporting by Will Dunham; Editing by Paul Simao)
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