The story behind the discovery that turned archaeology on its head
The discovery of an ancient engraving on a half a million-year-old shell happened by chance, says archaeologist José Joordens. She led the investigation into the oldest engraving ever found. What is the story behind this discovery?
Until now, the oldest known human engraving was a 100,000-year-old engraving on a piece of ochre, manufactured by Homo sapiens (modern man). José Joordens, lead author of the article that appeared in Nature on 3 December, says: ‘It suddenly appears that Homo erectus was more capable than we thought. Current archaeological assumptions about these early humans, who lived from 1.9 million to 400,000 years ago, will have to be revised.’
The discovery happened by ‘pure chance’, says the Leiden archaeologist. In 2007, she was studying some fossilised fish and shells in the depot of the Naturalis Biodiversity Centre in Leiden and she stumbled upon some fossilised freshwater shells from Java, which had been collected at the end of the 19th century by the Dutch physician Eugène Dubois. This shell collection had not been thoroughly examined since the 1930s, says Joordens. On Java, Dubois hadalso found a number of bones and skull fragments which were later attributed to Homo erectus. The shells intrigued Joordens and she invited Australian biological anthropologist Stephen Munro, who happened to be in the Netherlands at the time, to have a look at the collection.
Munro photographed the shells, but it was only back home in Australia that he noticed that one shell looked very peculiar: a very regular ‘zigzag pattern’ appeared on the outside. He sent the photograph to Joordens and this got the ball rolling. The archaeologist showed the photograph to a number of her colleagues, but none of them had ever seen such a pattern before. ‘This was when we began to suspect that there might be something remarkable going on,’ Joordens explained.
The shell was examined in more detail with an electron microscope capable of the highest magnification. This revealed how strongly the crystals of the calcium carbonate were blunted in the grooves, an indication that the scratches were very old. By using dating methods on the sediment (sand, clay, volcanic material) in the shell, it was established that the engraved shell must be between 430,000 and 540,000 years old.
Thanks to the magnifications and comparative research, the researchers were able to exclude the possibility that the pattern was caused by erosion or animals. Joordens: ‘The pattern is too regular and too ‘human’ for that. Our team also tried to recreate a similar engraving on a shell, and it was not easy to do. ‘The pattern must have been created by a strong and skilful tool-maker. That says a lot about the skills of Homo erectus.’
The engraving was by no means the team’s only discovery. Their investigation also revealed that early humans on Java used the shells of freshwater mussels as knives and scrapers. This insight is also remarkable: until now it was suspected, but never proven, that shells were used as tools.
Wil Roebroeks, Leiden Professor of Palaeolithic Archaeology, was able to finance this research with the Spinoza Prize he was awarded in 2007 by the NWO. ‘This kind of freely disposable funding is crucial for this type of research,’ he argues. Thanks to his prize, what began as a stroke of luck for a few researchers grew into a substantial international research team that is currently carefully re-examining the hundreds of fossilised shells from the Dubois Collection.
The team, which consists not only of archaeologists, but also of shell experts, geologists and biologists, also presented other findings in their Nature article, such as the fact that Homo erectus on Java not only used freshwater mussels as tools, but also ate them.
There is also new information regarding the age of Trinil, the site on Java where these remains of Homo erectus were found. In the past, researchers had estimated Trinil to be approximately 900,000 to 1.5 million years old. Joordens and her colleagues have adjusted this dating: the site is younger and is approximately half-a-million years old. Roebroeks: ‘It is thanks to those zigzag scratches that the story appeared in Nature, but there is so much more essential information here: about the diet of early humanoids, about the human remains found at Trinil, about the age of the site. This would have required at least four separate articles.’
The investigation is far from being completed, says Joordens. ‘Our results have led to a renewed interest in traces of Homo Erectus on Java. New generations of archaeologists and geologists are once again collaborating with Indonesian and foreign researchers. Who knows what else they will discover.’
The shell with engraving is on display at the Naturalis museum in Leiden from 4 December onwards.
(3 December 2014)