For many years, paleoanthropologists assumed that Homo habilis was the first human. As additional fossils were found, however, it became apparent to some researchers that there were two early humans. The first evidence of this, in the form of a skull designated as KNM-ER 1470, was found at Koobi Fora, on the eastern side of Lake Turkana (formerly Lake Rudolph). This skull was found by Richard Leakey and classified initially as Homo habilis. With additional finds in the area, some scientists suggested that there were two Homo species and KNM-ER 1470 should be classified as Homo rudolfensis, a designation first proposed in 1986.
The fossil remains of Homo rudolfensis found in the Lake Turkana region of Kenya were dated to about 2.5 to 1.9 million years ago. These dates show that Homo rudolfensis was contemporary with Homo habilis.
Homo rudolfensis had a cranial capacity of about 788 cc, somewhat larger than that of Homo habilis. There is a marked constriction of the braincase behind the eye sockets.
Homo rudolfensis had a relatively flat, broad face and fairly large teeth. In their chapter in The Oxford Handbook of Language Evolution Bernard Wood and Amy Bauernfeind report:
“The more primitive face of H. rudolfensis is combined with a robust mandible, and mandibular postcanine teeth with larger, broader, crowns, and more complex premolar root systems than those of H. habilis.”
In his chapter in The Oxford Companion to Archaeology Leslie Aiello writes:
“Although it has a larger brain size than H. habilis, it also has larger teeth and a face that retains some australopithecine features.”
These australopithecine features suggest to some researchers that Homo rudolfensis should actually be classified as Australopithecus rudolfensis. In his book The Story of the Human Body: Evolution, Health, and Disease, Daniel Lieberman writes:
“As far as we can tell, H. rudolfensis had a slightly larger brain than H. habilis, but its teeth and face were larger, flatter, and more like those of australopiths. It is plausible that H. rudolfensis was a large-brained Australopithicus and not actually a member of the genus Homo.”
There are some researchers who feel that Homo rudolfensis evolved from Kenyanthropus platyops and should be classified as Kenyanthropus rudolfensis. In their book The Complete World of Human Evolution, Chris Stringer and Peter Andrews write:
“Equally, the large face, back teeth, and thick jaws of rudofensis do not look particularly human, and some scientists have made an evolutionary link with the 3.5-million-year-old form called Kenyanthropus platyops, implying these might represent an entirely separate and extinct hominin lineage.”
In his book Humans: From the Beginning , Christopher Seddon writes:
“The existence of Homo rudolfensis as a separate species has remained controversial, although fossils recovered at Koobi Fora in 2012 are said to confirm its distinctiveness from Homo habilis.”
The increasing data from this early era of human evolution—fossils and stone tools—do not clarify which of these humans, Homo habilis or Homo rudolfensis, might be ancestral to modern humans. At best, we can simply say that both lived at approximately the same time.
Human origins
Human Origins: Homo habilis
Human Origins: Making Spoken Language Possible
Human Origins: Eyes
Human Origins: Protolanguage
Human Origins: Teeth
Human Origins: Humans as naked apes
Human Origins: Sex
Human Origins: Cultural Evolution