Taking a 3-D view of an ancient brain
Rebecca C. Jernigan
Studying the evolution of the human brain can provide researchers with insight into the developmental path of language and intelligence. It is possible to use an endocast — the impression taken from the inside of the cranium that retains the surface features of the brain — to learn about the brain structures of humanity’s ancient ancestors.
Unfortunately, many of the hominin fossils that have been discovered are incomplete or are filled with a heavy calcified matrix, making it difficult or impossible to reconstruct the endocasts without damaging the fossils. The Homo Liujiang skull, discovered in 1958 in Liujiang, Guangxi, China, is the most complete and best preserved late-Pleistocene human fossil to be found in southern China, but it is filled with a matrix that prevents conventional examination of its interior.
Researchers from the Chinese Academy of Sciences in Beijing, led by Xiujie Wu, examined the endocast of the Liujiang cranium in three dimensions using high-resolution industrial computed tomography (CT). Although CT has been used to examine fossils since the early 1980s, it rarely has been used to investigate those found in China.
Researchers used computed tomography to scan and digitally visualize a hominin skull. A virtual 3-D representation of the skull and the endocast is on the left. On the right are images of the extracted virtual endocast from various angles. Image courtesy of Xiujie Wu.
The investigators processed the scanned slice data with 2-D reconstruction software created at the academy’s Institute of High Energy Physics. They manually removed the interior matrix from the fossil in the images and transformed the scans into a 3-D model. Nine standardized measurements and 11 landmarks were chosen, measured and compared with the same marks and measurements on 15 other skulls, including fossils from China, Indonesia, Europe and Africa, as well as a modern Chinese cranium.
Despite the age of the Liujiang cranium, which is somewhere between 40,000 and 220,000 years old, depending on the source, the brain morphology that can be inferred from its endocast has more in common with the modern Chinese skull than with the more primitive fossils.
Interestingly, the Liujiang fossil has a cranial capacity of 1567 cc, well within the normal range (1300 to 1750 cc) of modern human brain size.
Chinese Science Bulletin, January 2008, pp.2513-2519.
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