Re-creating ancient hominid virtual endocasts by CT-scanning.

Probably the first radiographic study of human fossils, that by D. Gorganovic-Kramberger on Neandertal remains from Krapina, Croatia, was published in 1906, only 11 years after Röntgen announced the discovery of X-rays. Many subsequent studies on fossil hominids used regular clinical diagnostic radiological apparatus, as depicted in Atlas of Radiographs of Early Man by M.F. Skinner and G.H. Sperber (1982). Some specimens such as crania filled with heavily calcified matrix proved intractable. Ordinary radiographs of such specimens usually failed to reveal endocranial structure, as fossilized bone and calcified endocast were approximately equally radio-opaque. Thus, neither endocranial volume nor structural details were detectable. The only invasive method that could have been employed involved mechanical removal of the solid matrix, but this entailed hazards to the cranial vault and the destruction of the natural endocranial cast. In 1983--1984, G.C. Conroy and M. Vannier utilized recent advances in high-resolution computed tomography to produce non-invasive, intracranial capacity measurements of matrix-filled fossil skulls. They tried the method on two fossil mammal skulls filled with hard sandstone matrix (1984, Science 26:456-458), and then successfully applied it to a South African, matrix-filled cranium of the ancient hominid (hominin) species, Australopithecus africanus from Makapansgat (Conroy et al. 1990, Science 247:838-841). Details of the morphology of the endocranial surface of the braincase were revealed, including the pattern of venous sinus drainage in the posterior cranial fossa. A group based in St. Louis, Vienna, Paris, Rome, and Johannesburg has taken such studies further. Beautiful "virtual endocasts" have been produced on a large male specimen of A. africanus from Sterkfontein, South Africa, and the endocranial capacity has been determined (1998). The methods make it possible to re-create "virtual endocasts" of ancient hominids.