August 09, 2012

Multiple species of early Homo

I will point you towards Hominid Hunting, the NY Times, and Nature for coverage of the paper. From the press release:
Found within a radius of just over 10 km from 1470's location, the three new fossils are dated between 1.78 million and 1.95 million years old. The face KNM-ER 62000, discovered by field crew member Elgite Lokorimudang in 2008, is very similar to that of 1470, showing that the latter is not a single "odd one out" individual. Moreover, the face's well-preserved upper jaw has almost all of its cheek teeth still in place, which for the first time makes it possible to infer the type of lower jaw that would have fitted 1470. A particularly good match can be found in the other two new fossils, the lower jaw KNM-ER 60000, found by Cyprian Nyete in 2009, and part of another lower jaw, KNM-ER 62003, found by Robert Moru in 2007. KNM-ER 60000 stands out as the most complete lower jaw of an early member of the genus Homo yet discovered.
I'm not competent enough to express an opinion, so I won't. Still, if there were two species living at that time, it would not be surprising; in the recent past where we do have more complete data, it seems that our Homo sapiens ancestors shared the planet with other quite divergent hominins. Perhaps this was the norm for the greater part of human prehistory, until evolution came up with us, and we came up with ideas (whether through love or war) to drive the rest of Homo to non-existence, leaving us as the only living twig of a quite bushy family tree.

Nature 488, 201–204 (09 August 2012) doi:10.1038/nature11322

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

Since its discovery in 1972 (ref. 1), 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 epoch2 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 roots3. 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 factors4, 5, 6, 7, 8, 9, or whether it provides evidence of species diversity marked by differences in cranial size and facial or masticatory adaptation3, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20. 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.



andrew said...

The Hominid Hunting post does a much better job of explaining the context of why this find is important than any of the other links.

I'd just love to see side by side artists representations of the three Homo species that apparently coexisted: Habilis (aka Lucy), Rudolfensis (the parallel species whose existence of the new finds favors), and Erectus (e.g. Java Man).

Pictures limited merely to reassembled bones are hard for people who haven't done graduate work in this kind of thing to translate mentally into how a living breathing hominid of that species would look. How can someone like myself imagine what these skulls would look like with flesh on them when I have trouble doing that for even plain vanilla Homo Sapiens?

terryt said...

"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".

Or one very geographically variable species?

terryt said...

John Hawks seems to caution much the same view:

"I think it is premature to sort these East African fossils into four or more species on the basis of one or two new specimens".

Interestingly he has been talking to Lee Berger, a scientist not commanding much respect these days. But years ago he delivered a paper on regional diversity in Australopithecus. It would be interesting to see that paper resurrected.