Newly discovered fossils of 'Homo rudolfensis' suggest 'Early man was not alone'

In general, all non-australopithecine remains from Olduvai Gorge have been assigned to Homo habilis, whereas those from Lake Turkana are attributed to either Homo habilis or Homo rudolfensis.

The type specimen of Homo rudolfensis is Skull 1470 (KNM-ER 1470) found by Bernard Ngeneo at Koobi Fora* in 1972, on the eastern shore of Lake Rudolf, now Lake Turkana, in northwestern Kenya (Leakey et al. 1973). He was working at the time with a group led by Richard and Meave Leakey. The specimen has an age of at least 1.89 million years, although it was initially assigned a far earlier date in error — 3 mya, at the time earlier than any australopithecines known. The result was a storm of debate.

Since it was found 45 m below the KBS tuff, which is known to date to 1.89 mya, the skull may be significantly older than the tuff itself. Conceivably, it could date back to as early as 2.5 mya, which would make it contemporary with the earliest H. habilis specimens. There is no postcranial material known. Nor has much been ascertained about the diet of this hominid on the basis of tooth wear due to the paucity of available fossil remains.

Originally, Skull 1470 was described as Homo habilis, and was first assigned to a newly erected Homo rudolfensis only in 1986. This arrangement has seen increasing favor, but in the last few years some researchers have asserted that 1470 is similar to the more recently discovered fossil KNM-WT 40000, Kenyanthropus platyops (Leakey et al. 2001), and that it should be reclassified as such. However, other specimens, mostly mandibles, have been tentatively assigned to Homo rudolfensis (see table at right). Moreover, it has been questioned whether Kenyanthropus platyops is actually distinct from the contemporaneous Australopithecus afarensis.

Initially, the cranial capacity of KNM-ER 1470 (which stands for Kenya National Museum-East Rudolf) was estimated at 752 cc. But Bromage et al. (2008) reevaluated the skull and moderately reduced the brain-size estimate to 700 cc.

Many paleoanthropologists still do not accept Homo rudolfensis as a valid, distinct type of hominid. Is it, or isn't it? That no doubt will remain the question for some time to come!