Oldest known engraving (Trinil shell)

A freshwater mussel shell collected at Trinil, Java, by Eugène Dubois in the 1890s lay unnoticed in a museum collection in Leiden for more than a century. In 2014 a research team led by Josephine Joordens published a study of this shell and found, on its surface, a zigzag pattern of lines. Dating of the surrounding sediments placed the shell at about 430,000 to 540,000 years old. The lines are the oldest known engraving by a human ancestor, made by Homo erectus, long before modern humans arrived in Southeast Asia.

The scientists tested whether the marks were natural damage and found they were deliberate: the lines cross each other in a regular pattern, and the shell was fresh at the time, still held together by its ligament, and they were cut with a sharp object. Experiments with a shark tooth, which are present in the same site's deposits, produced similar scratches. The mussel was probably opened with the same kind of tool and eaten. Nobody knows whether the pattern had a meaning, was decoration, or was just doodling. The find suggests Homo erectus could carry out controlled, repeated, abstract marking, in addition to making stone tools, and that symbolic behavior has deeper roots than once thought.