Homo rudolfensis

Homo rudolfensis is a controversial taxon proposed in 1986 by Soviet anthropologist Valery Alekseyev for the old fossil hominin skull KNM-ER 1470. The skull is believed to be 1.9 million years old and was recovered in 1972 at Koobi Fora on the eastern shore of Lake Turkana (then Lake Rudolf), Kenya. The skull had previously been assigned to Homo habilis, but Alekseyev proposed reassigning it to a new species on the basis of morphological differences, most significantly a cranial capacity which, at 750cc, was significantly larger than that of H. habilis (approx 600-680cc). It also had a flatter, broader face and broader post-canine teeth (molars and premolars), with more complex crowns and roots, and thicker enamel. Subsequently other fossils including mandibles and cranial fragments, all located at Lake Turkana, were assigned to the new species and there is a roughly 50/50 split between H. habilis and H. rudolfensis remains at this site.

Cameron & Groves (2004) reject Homo status altogether for KNM-ER 1470. By phylogenetic analyses of hominin craniofacial morphology, they demonstrated that the australopithecine-like species Kenyanthropus platyops (“flat-faced man of Kenya”), a contemporary of Australopithecus afarensis (“Lucy”), was probably ancestral to KNM-ER 1470 and suggested that Homo rudolfensis should be reclassified as Kenyanthropus rudolfensis.

Homo rudolfensis’ claims as a possible ancestor to modern humans received a further blow in 2007 when KNM-ER 1470 was reconstructed by anthropologist Timothy Bromage of the New York University. Bromage noted that the jaw had been positioned incorrectly and actually jutted out further than originally believed. He downsized the cranial capacity to 526cc, below that of Homo habilis. The reconstructed skull more closely resembles those of Australopithecus (gracile australopithecines) or Paranthropus (robust australopithecines) than those of Homo (humans).

Dr. Bromage’s conclusions are not universally accepted, but if correct they would reinforce the outcome of the Cameron & Groves study.

References:

Bromage T (2007): Craniofacial Architectural Constraints Resolve Major Quandry of Human Evolution, presentation to NYUCD, released 26 March 2007.

Cameron D & Groves C (2004): Bones, Stones and Molecules: “Out of Africa” and Human Origins, Elsevier Academic Press.

© Christopher Seddon 2009