| Homo rudolfensis Temporal range: Pleistocene, 1.9 MaPreЄ Є O S D C P T J K Pg N ↓ | |
|---|---|
| Reconstruction of the KNM ER 1470 skull | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Primates |
| Family: | Hominidae |
| Genus: | Homo(?) |
| Species: | H. rudolfensis |
| Binomial name | |
| †Pithecanthropus rudolfensis Alekseyev, 1978[1] | |
Homo rudolfensis (also Australopithecus rudolfensis) is an extinct species of theHominini tribe known only through a handful of representative fossils, the first of which was discovered by Bernard Ngeneo, a member of a team led by anthropologist Richard Leakeyand zoologist Meave Leakey in 1972, atKoobi Fora on the east side of Lake Rudolf (now Lake Turkana) in Kenya.
The scientific name Pithecanthropus rudolfensis was proposed in 1978 by V. P. Alekseyev[1] who later (1986) changed it to Homo rudolfensis[2] for the specimen Skull 1470 (KNM ER 1470). It remains an open question whether the fossil evidence is sufficient for postulating a separate species, and if so whether this species should be classified as within the Homo orAustralopithecus genus.
On 8 August 2012, a team led by Meave Leakey announced the discovery of a face and two jawbones belonging to H. rudolfensis.
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Homo habilis vs.Homo rudolfensis[]
Comparisons between fossil OH 24, recognized as a Homo habilis skull discovered by Peter Nzube, along with the female H. habilis fossil KNM ER 1813, and KNM-ER 1470 (male) have brought much controversy as to whether H. rudolfensis and H. habilisshould be classified as two separate species or lumped together into H. habilis.
When compared to other older H. habilisfossils like OH 24, the mandible and jaw of ER 1470 do not fit within the limits of variation of H. habilis.[6] KNM-ER 1470 displays less prognathism and a rounder brain case. After much debate, but no clear settlement, fossil KNM ER 1813 was found in 1973 by Kamoya Kimeu, which helped settle some disputes regarding the H. habilis and H. rudolfensis species. When compared to ER 1813, ER 1470 manifests a larger braincase ranging from 750-800ml.[7]
Even if sexual dimorphism were considered, the size difference in the mandible and teeth would be too great compared to KNM-ER 1813. Fossil KNM-ER 1470, a male H. rudolfensis, has massive teeth in comparison to the female H. habilis fossil KNM-ER 1813 and portrays a much larger brain case than KNM-ER 1813. When KNM-ER 1813 and KNM-ER 1470 are compared to OH 24, similarities between OH 24 and KNM-ER 1813 are more widely evident than with KNM-ER 1470. These similarities include smaller orbits, the projection of the mid-face below the nose and a smaller skull size over all. The assumed ages of these three fossils, the places where they were found and some of the anatomical similarities between them leads many scholars to assume that the two species – H. habilis and H. rudolfensis – co-existed somewhere in the East African area sometime between 2.0 and 1.5 million years ago along with Homo erectus and Paranthropus boisei.
2012 fossil find[]
In August 2012, a team led by Meave Leakey published an academic paper inNature announcing three additional H. rudolfensis fossils from northern Kenya had been found: two jawbones with teeth and a face.[8][9] The face (fossil KNM-ER 62000) was of a juvenile, but had features in common with KNM-ER 1470, suggesting that the latter skull's uniqueness is due to being a separate species, rather than a large male H. habilis.[10] Team member Fred Spoor described the face as "incredibly flat", with a straight line from the eye socket to the incisor tooth.[11] The jawbones, which appeared to match KNM-ER 1470 and KNM-ER 62000, were also shorter and more rectangular than known H. habilis specimens.[10]
The fossils were dated to about two million years ago, being contemporaneous with H. habilis.[11]According to Leakey et al., "the new fossils confirm the presence of two contemporary species of early Homo[that is, habilis and rudolfensis], in addition to Homo erectus, in the earlyPleistocene of eastern Africa".[9] Lee Rogers Berger, however, called the argument "weak", and proposed the finds be compared to other possibilities, such as Australopithecus africanus andAustralopithecus sediba.[11] Tim D. Whiteof the University of California also challenged the findings, asking, "How can practitioners in this field possibly expect to be able to accurately identify fossil species based upon a few teeth, jaws, and lower faces in light of what we know about the great variation found among different individuals in a single living species?" Leakey replied, "I would challenge Tim to find any primate in which you would see the same degrees of variation as those that we are seeing between our new fossils and KNM-ER 1802".[12] KNM-ER 1802 is a lower-jawfossil that is thought to be of a Homo rudolfensis. Given the difference between this fossil and the ones found in 2012, Leakey has proposed that the fossil is not of a H. rudolfensis, but possibly, of a H. habilis. Bernard Wood considers that it is "perfectly possible" that there were interactions between these different species.[12]