http://www.livescience.com/22198-new-human-species-discovered.html
New fossils from the dawn of the human lineage suggest our ancestors may
have lived alongside a diversity of extinct human species, researchers say.
...
Now fossils between 1.78 million and 1.95 million years old discovered in
2007 and 2009 in northern Kenya suggest that early Homo were quite a
diverse bunch, with at least one other extinct human species living at the
same time as H. erectus and H. habilis.
"Two species of the genus Homo, our own genus, lived alongside our direct
ancestor, Homo erectus, nearly 2 million years ago," researcher Meave
Leakey at the Turkana Basin Institute in Nairobi, Kenya, told LiveScience.
A skull known as KNM-ER 1470, found in 1972 in Kenya, was at the center of
the debate over the number of species of early Homo living nearly 2 million
years ago. It had a larger brain and a flatter face than H. habilis, leading
some researchers to declare it a distinct species they dubbed Homo
rudolfensis.
However, making comparisons between these fossils was difficult, because no
single purported H. rudolfensis specimen contained both the face and the
lower jaw, details needed to see if it was indeed separate from H. habilis.
Any supposed differences between H. habilis and H. rudolfensis might, for
instance, have been due to variations between the sexes of a single species.
The newly discovered face and lower-jaw fossils, uncovered within a radius
of just more than 6 miles (10 kilometers) from where KNM-ER 1470 was
unearthed, now suggest that KNM-ER 1470 and the novel finds are indeed members
of a distinct species of early Homo that stands out from others with its
uniquely built face.
"It had very flat facial features — you could draw a straight line from its
eye socket to where its incisor teeth would be," researcher Fred Spoor at the
Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, told
LiveScience.
...
"The incisors are really rather small compared to what you'd find in other
early Homo," Spoor said. "In the back of the mouth, the teeth are large,
telling us a lot of food processing was going on there ... it may be possible
it ate more tough, plantlike foods than meat."
...
http://www.nature.com/nature/journal/v488/n7410/full/nature11322.html
New fossils from Koobi Fora in northern Kenya confirm taxonomic diversity in early
Homo
Meave G. Leakey, Fred Spoor, M. Christopher Dean, Craig S. Feibel,
Susan C. Antón, Christopher Kiarie & Louise N. Leakey
Nature 488, 201–204 (09 August 2012) doi:10.1038/nature11322
Since its discovery in 1972, the cranium KNM-ER 1470 has been at the centre
of the debate over the number of species of early Homo present in the early
Pleistocene epoch of eastern Africa. KNM-ER 1470 stands out among other
specimens attributed to early Homo because of its larger size, and its flat
and subnasally orthognathic face with anteriorly placed maxillary zygomatic
roots. This singular morphology and the incomplete preservation of the
fossil have led to different views as to whether KNM-ER 1470 can be
accommodated within a single species of early Homo that is highly variable
because of sexual, geographical and temporal factors, or whether it provides
evidence of species diversity marked by differences in cranial size and
facial or masticatory adaptation. Here we report on three newly discovered
fossils, aged between 1.78 and 1.95 million years (Myr) old, that clarify
the anatomy and taxonomic status of KNM-ER 1470. KNM-ER 62000, a
well-preserved face of a late juvenile hominin, closely resembles KNM-ER 1470
but is notably smaller. It preserves previously unknown morphology, including
moderately sized, mesiodistally long postcanine teeth. The nearly complete
mandible KNM-ER 60000 and mandibular fragment KNM-ER 62003 have a dental
arcade that is short anteroposteriorly and flat across the front, with small
incisors; these features are consistent with the arcade morphology of KNM-ER
1470 and KNM-ER 62000. The new fossils confirm the presence of two
contemporary species of early Homo, in addition to Homo erectus, in the early
Pleistocene of eastern Africa.