“Now, after 7 years of work on the shells, Munro and colleagues have confirmed their observations. They also report that one of the shells was used as a tool of some sort, a finding that would expand the known toolmaking capabilities of H. erectus, which was thought to have made only simple tools out of stone.
“If correct it certainly pushes back in time the evidence for marking objects in a way that arguably could be considered evidence for symbolic activity,” says Curtis Marean, an archaeologist at Arizona State University, Tempe, who was not involved in the study. But he points out that the Java site, known as Trinil, was excavated in the 1890s using “quite primitive” archaeological methods and that no one has reexamined the location using modern techniques. That means, he says, that “the observation is essentially devoid of context.”
“Mindful of this kind of criticism, archaeologist and team leader Josephine Joordens of Leiden University in the Netherlands says her group took its time answering a series of questions about how the shell came to be engraved as well as when it might have happened. First, the researchers looked at how the shells accumulated at Trinil in the first place. Munro had focused his research on about 166 specimens of the freshwater mollusk Pseudodon, collected by Dutch paleoanthropologist Eugène Dubois at the site where he found now-famous H. erectus fossils.
Studying cigar boxes full of mollusks from the site that are now housed in Leiden, Joordens and other team members found that a third of the shells had holes right where a muscle that keeps the shell closed is found. These holes were apparently made by humans using shark teeth, also found at the site, as tools to open the shells so they could eat them; when team members did their own experiments trying to open shells with sharks’ teeth, they got a very similar pattern of holes….”