Researchers say a sharp zigzag, engraved into the underside of a shell, is the oldest example of human art.

Previously, the earliest examples of geometric art were determined to be roughly 100,000 years old, found in South Africa. But a number of dating tests suggests the ancient shell found on the island of Java was engraved between 430,000 and 540,000 years ago.

"It's at least four times as old," Josephine Joordens, a researcher at Leidens University in the Netherlands, told NPR.

Not only does the new discovery push back human creativity a few hundred thousand years, it pushes it back a few evolutionary leaps.

"Also, we are not talking now about our own species, modern humans, but we are talking about Homo erectus, a species that's older even than Neanderthals," Joordens said. "It's putting the origin of such engraving behavior a lot farther back in time."

The shell was the first engraving excavated from an Indonesian riverbank by Eugene Dubois, a 19th century Dutch scientist keen on the theory of human evolution. Dubois most famously led the expedition that uncovered the first Homo erectus specimen -- an early human species that lived more than a million years ago. The ancient shell has been sitting in a natural history museum in the Netherlands for more than a century.

Joordens and a team of 20 other researchers have been studying the shell for the last seven years, trying to account for any other explanation for its engraving. In their latest paper on the subject -- published this week in the journal Nature -- the researchers conclude that only a human could have made the zigzag.

"I can imagine people may be wondering whether this can be seen as a form of early art," Wil Roebroeks, an archaeologist at Leiden University, said of the new findings. "At the moment we have no clue about the meaning or purpose of this engraving."