Archaeologists studying freshwater mussel shells excavated in the nineteenth century at Trinil, Java, have discovered geometric patterns carved by Homo erectus 500,000 years ago and unambiguous evidence that one shell had been sharpened and polished for use as a cutting tool. In addition, the number of large adults in the shell assemblage suggests that they were intentionally collected for eating.
The shells were excavated by Dutch anthropologist Eugene Dubois in 1891 during the course of his work in Java, which led to the discovery of Homo erectus. They now form part of the Dubois Collection in the Naturalis Biodiversity Centre in Leiden. Researchers dated sediments within the shells with argon-argon and luminescence methods to obtain an age range of 540,000 to 430,000 years old.
The engraved shell, designated DUB1006-fL, displays a geometric pattern of grooves. The pattern consists of a zigzag line with three sharp turns producing an ‘M’ shape, a set of more superficial parallel lines, and a zigzag with two turns producing an inverted ‘N’ shape. The grooves appear to have been intentionally produced, and comparison with experimentally-made grooves suggest that they were made with a shark tooth.
Previously, the earliest evidence for the carving of abstract patterns was the engraved ochres from Blombos Cave, South Africa, which date from the period 100,000 to 75,000 years ago, and the 60,000 year old engraved ostrich shells from Diepkloof Cave, South Africa. Neanderthals made abstract rock engravings at Gorham’s Cave, Gibraltar, 39,000 years ago. More controversially, it has been suggested that a 230,000 year old pebble found at Berekhat Ram in the Golan Heights is a representation of the female form.
The cutting tool is the earliest-known example of the use of shells for tool-making, and may have been a response to the lack of locally-available material for making stone tools. A similar explanation has been proposed for Neanderthal shell tools from Italy and Greece, but these are only around 110,000 years old.
Finally, seafood is a dietary adaptation was once thought to be exclusive to modern humans, beginning around 165,000 years ago. Subsequently it was discovered that Neanderthals were exploiting seafood on the Malaga coast 150,000 years ago. The Trinil shells show that the use of seafood by humans was a much earlier development.
Overall, the Trinil shells suggest that Homo erectus possessed a far greater behavioural flexibility than previously believed in terms of both tool-making technology and subsistence strategies. The engraved geometric pattern suggest that at least some capacity for symbolic thought was already present in early humans 500,000 years ago.
The findings are published in the journal Nature.
1. Joordens, J. et al., Homo erectus at Trinil on Java used shells for tool production and engraving. Nature (2014).