In 1973, Mr. Leakey had reconstructed the skull KNM-ER 1470 with a flat face and a brain volume of . In 1983, American physical anthropologist Ralph Holloway revised the base of the skull and calculated a brain volume of . For comparison, "H. habilis" specimens average about , and "H. ergaster" . Anthropologist Timothy Bromage and colleagues revised the face again at a 5° incline (slightly prognathic) instead of completely flat, but pushed the nasal bone back directly beneath the frontal bones. He then said it was possible to predict brain size based on just the face and (disregarding the braincase) calculated , and chalked up the errors of Leakey's reconstruction to a lack of research of the biological principles of facial anatomy at the time as well as confirmation bias, as a flat-faced reconstruction of the skull aligned with the predominant model of human evolution at the time. This was refuted by American palaeoanthropologist John D. Hawks because the skull remained more or less unchanged except for the 5° rotation outwards. Bromage and colleagues returned in 2008 with a revised skull reconstruction and brain volume estimate of .