Homo erectus on Java was already using shells of freshwater mussels as tools half a million years ago, and as a 'canvas' for an engraving. An international team of researchers, led by Leiden archaeologist José Joordens, published this discovery on 3 December in Nature. "Until this discovery, it was assumed that comparable engravings were only made by modern humans (Homo sapiens) in Africa, starting about 100,000 years ago," says lead author José Joordens, researcher at the Faculty of Archaeology at Leiden University.
     A team of 21 researchers studied hundreds of fossil shells and associated finds and sediments from the Homo erectus site Trinil, on the Indonesian island of Java. The shells were excavated by the Dutch physician and researcher Eugène Dubois, the discoverer of Pithecanthropus erectus - now known as Homo erectus.
     The discovery of an engraved geometrical pattern on one of the shells came as a total surprise. The zig zag pattern, that can only be seen with oblique lighting, is clearly older than the weathering processes on the shell arising from fossilisation. The study has excluded the possibility that the pattern could have been caused by animals or by natural weathering processes and shows that the 'zigzag' pattern is the work of Homo erectus.
     By applying two dating methods, researchers at the VU University Amsterdam and Wageningen University have determined that the shell with the engraving is minimally 430,000 and maximally 540,000 years old.This means that the engraving is at least four times older than the previously oldest known engravings, found in Africa. It is not clear whether the pattern was a form of art, or served another purpose.
     Other experts expressed scepticism about the research. John Shea, from Stony Brook University in New York, said there was "nothing like it around for hundreds of thousands of years, and thousands and thousands of miles. If this is symbolic behaviour by Homo erectus, then it's basically the only evidence we've got for a species that lived for a million-and-a-half years on three continents".
     This research has shown that these early human-like people were very clever about how they opened these large freshwater mussels; they drilled a hole through the shell using a sharp object, possibly a shark's tooth, exactly at the point where the muscle is attached that keeps the shell closed. "The precision with which these early humans worked indicates great dexterity and detailed knowledge of mollusc anatomy," says Frank Wesselingh, a researcher and expert on fossil shells at Naturalis Biodiversity Center. The molluscs were eaten and the empty shells were used to manufacture tools, such as knives.
Possible follow-on research
     This discovery sheds unexpected new light on the skills and behaviour of Homo erectus, and indicates that Asia is a promising and, so far, relatively unexplored area for finding intriguing artefacts. The shell with the oldest known human engraving will be on display in the Naturalis museum from 4 December onward.

Edited from Nature, ScienceDaily (3 December 2014), BBC News (4 December 2014)