A shell found in the 1890s and reexamined in 2007 contains drawings made about half a million years ago – 300,000 years before man evolved to Homo sapiens.

The ancient mollusk has arrow-shaped markings on its shell that were made deliberately by Homo erectus, New Scientist reports.

Dutch geologist Eugene Dubois initially found the shell in Trinil, Indonesia over 200 years ago. In addition to a host of other shells, other fossils found in the area include several animal and Homo erectus bones.

The shell collection remained in a museum in the Netherlands until archaeologist Josephine Joordens of the University of Leiden took another look at the specimens. Dr Stephen Munro – then a doctoral student at the Australian National University in Canberra – was encouraged to examine the shells as well, and photographed each fossil before going back to Australia.

"A week later I received an email," Joordens told New Scientist. "He wrote that there was something strange on one of the shells and did I know what it was?"

Joordens' team removed tiny pieces of sediment from the cracks and grooves of the shell to reveal tiny arrow marks.

University of Bordeaux paleoanthropologist Francesco d'Errico used flint, a shark's tooth, and a steel scalpel to replicate the etchings, and discovered that the marks were caused deliberately, and did not serve any obvious function. Also, the drawings would have been stark white on the fresh shell's dark brown coat, further implying that the marks were a form of decoration.

University of St Andrews psychologist and primatologist Andrew Whiten marvelled at the implication.

"It's very carefully done," he said. "There is a wonderfully straight section and the [etch] turns in one continuous line. That's not just intentional but careful in what strikes as a very modern way. Apes aren't doing that. It would be staggering if they did."

All of the shells in the collection were buried at the same time between 430,000 and 540,000 years ago, indicating that a volcanic eruption or flash flood had covered the mollusks.

"It is a fascinating discovery," University of Cambridge archaeologist Colin Renfrew admitted. "The earliest abstract decoration in the world is really big news."