Originally thought to be a member of the species Homo habilis, the fossil was the center of much debate concerning its species. Assigned initially to Homo habilis, the skull was at first incorrectly dated at nearly three million years old. The differences in this skull, when compared to others of the Homo habilis species, are too pronounced, leading to the presumption of a Homo rudolfensis species, contemporary with Homo habilis. It is not certain if H. rudolfensis was ancestral to the later species in Homo, or if H. habilis was, or if some third species yet to be discovered was.
In March 2007, a team led by Timothy Bromage, an anthropologist at New York University, reconstructed the skull of KNM-ER 1470. The new construction looked very ape-like (possibly due to an exaggerated rotation of the skull) and the cranial capacity based on the new construction was reported to be downsized from 752 cm³ to about 526 cm³, although this seemed to be a matter of some controversy. Bromage published his results in 2008 where the cranial capacity was now estimated at 700 cm³. Bromage said his team’s reconstruction included biological principles not known at the time of the skull’s discovery, which state that a mammal’s eyes, ears and mouth must be in precise relationships relative to one another.