The world's oldest artwork, dated to 540,000 years ago, was created using one or more shark teeth, as well as a mollusk shell, according to a new finding. The art itself consists of etchings on a pale shell, which pushes back the history of art by hundreds of thousands of years.

The shell, along with the ancient artwork, was first collected on the island of Java in Indonesia over a century ago. Members of Homo erectus, an early human ancestor, lived on the island, beginning more than one million years before our time.

Stephen Munro was a graduate student in archaeology who was studying the 100-year-old collection of seashells in 2007, when he discovered the abstract etchings. The oldest known artwork at that time was dated to just 100,000 years before the modern age. Moreover, those pieces were created by anatomically-modern human beings, leading researchers to the conclusion that only our species could create abstract art.

A study of the shells, performed over the course of seven years, has revealed one of the specimens in the collection was used as a tool, in order to etch other pieces. This shows Homo erectus was capable of creating more complex tools than the simple stone implements previously believed to be the limits of their ancient technology.

"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," Curtis Marean of the Arizona State University, Tempe, an archaeologist not involved in the study, said.

Josephine Joordens of Leiden University in the Netherlands led research on the shells, including determination of how the engravings were created. The first challenge was to figure out how the shells came to the region of Java where they were found. The team discovered holes in one-third of the specimens, located where a muscle keeps the bivalve closed. These holes were likely drilled using shark teeth, which were also found nearby. When investigators drilled through shells using shark teeth, they produced features in the shell similar to those seen in the ancient specimens. This evidence suggested the mollusks were gathered by human ancestors for food.

Other possible causes for the etchings were eliminated, including the possibility the markings were created by animals. Microscopic analysis of the etchings revealed a sharp tool was held tightly as corners were made in the etchings, which is inconsistent with an animal attack. Weathering in the etchings showed they were not created in the modern age.

The Trinil area of Java was excavated in the 1890s, using primitive techniques that did not ensure the specimens remained undamaged and uncontaminated during collection and transport.

Investigation of the ancient shells, revealing the first known art from a nonhuman ancestor, was detailed in the journal Nature.