Human ancestors engraved abstract patterns

A member of the now-extinct hominid species Homo erectus engraved a geometric design on a sea shell nearly half a million years ago, long before the earliest evidence of comparable etchings made by modern humans, researchers say.

Fossil mussel shells excavated more than a century ago at an H. erectus site on the Indonesian island of Java include a shell with engravings of an M shape, two parallel lines and a reversed N shape, the scientists report December 3 in Nature. Another shell contains an intentionally sharpened edge with a polished surface, indicating it was used as a cutting or scraping tool, they say.

Abstract and perhaps symbolic forms of thinking associated with such creations preceded the evolutionary origins of Homo sapiens around 200,000 years ago, say archaeologist Josephine Joordens of Leiden University in the Netherlands and her colleagues.

The oldest examples of engravings made by modern humans date to around 100,000 years ago (SN Online: 6/12/09). These consist of geometric designs and lines carved into pieces of pigment found in South Africa.

“If Homo erectus carved geometric designs into shells half a million years ago, then geometric engravings cannot be considered ‘modern human behavior,’ ” says archaeologist John Shea of Stony Brook University in New York. Scientific definitions of modern behavior have become increasingly meaningless, in his view.

Joordens’ team identified a single shell thought to have been decorated by H. erectus, a species that left no other evidence of symbolic marking from its 1.5 million years of wandering Africa, Asia and Europe, Shea cautions. And the engraved shell has sat in a museum for more than 100 years, raising the possibility that someone with access to the find could have carved the design. Only the discovery of a similarly marked shell at a new excavation will confirm H. erectus’ status as a carver of abstract designs, Shea says.

If the marks on the ancient shell were indeed made by H. erectus, then this new find also challenges conventional wisdom that behavioral innovations during the Stone Age occurred first in Africa and then spread elsewhere, says paleoanthropologist Bernard Wood of George Washington University in Washington, D.C.

Joordens and colleagues analyzed complete shells and other remains of 166 freshwater mussels originally unearthed at Java’s Trinil site in the 1890s. In addition to the engraved shell, one-third of the others contained small holes at an attachment location for a muscle that clamps shut the creature’s protective shells.

Experiments conducted by the researchers with living freshwater mussels indicate that H. erectus individuals used pointed objects — perhaps shark’s teeth, which were unearthed in the same sediment as mussel shells at Trinil — to pierce shells at spots where the muscle could be deactivated.     

Enough soil clung to the museum-held mussels for Joordens’ group to estimate ages for the finds. Measures of the age of volcanic ash in the soil indicate that the shells date to no more than 540,000 years ago. Measures of the time since the finds were covered by soil suggest the shells are no younger than 430,000 years old.

Previous estimates placed the Trinil discoveries at anywhere between 1.5 million and 700,000 years old.