Oldest engravings to date discovered on 500,000-year-old shells

living in Java, Indonesia, half a million years ago used freshwater shellfish for the production of tools and what appears to be art. These newly discovered engravings, described in this week, are the oldest ever found.

© Henk Caspers, Naturalis, Leiden, The Netherlands

Inside of the fossil Pseudodon shell (DUB7923-bL) showing that the hole made by Homo erectus is exactly at the spot where the adductor muscle is attached to the shell

We used to think that geometric engravings were a sure sign of modern cognitive abilities, and experts have long debated over the origins of these behaviors. "Until this discovery, it was assumed that comparable engravings were only made by modern humans - - in Africa, starting about 100,000 years ago," Josephine Joordens of Leiden University says in a news release. Not so, Asian appears to be fully capable of this "modern" behavior as well.

Analyzing hundreds of samples collected in the 1890s from the main bone layer (called Hauptknochenschicht) of the Trinil site in Java, Joordens, a large international team found evidence for the modification of the shells of a mollusk called Pseudodon. had a clever trick for opening these large freshwater mussels: They drilled a hole through the shell using a hard, pointed object (possibly a shark's tooth) at exactly the spot where the muscle that keeps the shell closed is attached. These are called adductor muscles, and once damaged, the bivalves open right up. After eating the mussels, they used the empty shells to manufacture tools or as a canvas for some prehistoric doodling. The sediment in the shells date to between 430,000 and 540,000 years ago.

One of the shells has a smooth and polished edge, which indicates that it was used as a tool for cutting or scraping. made this shell tool by modifying the ventral margin (or underside) of a Pseudodon shell (DUB5234-DL) pictured below (a). Below that is a detailed look at the sharp edge (b).

© Francesco d’Errico, Bordeaux University

Another shell has a zigzag pattern of grooves on it that's only visible now using light from an angle. The lack of gaps between the turns of the grooves suggests that the maker paid meticulous attention to detail - not to mention, it was very difficult to replicate the pattern on both fresh and fossilized shells (the researchers tried). "We are really certain that this must have been made by an agent who did a very deliberate action with a very sharp implement," Joordens tells . Possibly with something like the shark tooth used to open the mussel. Here's the fossilized Pseudodon shell (DUB1006-fL) with the engraving. A detailed close-up is on the right.

© Wim Lustenhouwer, VU University Amsterdam

So, it was purposeful, but can we actually call it art? "If you don't know the intention of the person who made it, it's impossible to call it art," she adds. "But on the other hand, it is an ancient drawing. It is a way of expressing yourself. What was meant by the person who did this, we simply don't know... It could have been to impress his girlfriend, or to doodle a bit, or to mark the shell as his own property."