The discovery of a fist-sized ceramic cylinder and fragments of engraved plaques has pushed back the earliest evidence of writing in the Americas by at least 350 years to 650 BC.

Rolling the cylinder printed symbols indicating allegiance to a king - a striking difference from the Old World, where the oldest known writing was used for keeping records by the first accountants.

Archaeologists uncovered the cylinder and fingernail-sized fragments among debris from an ancient festival at San Andres, an Olmec town on the coastal plain of the Mexican state of Tabasco.

Carbon dating of layers in the rubbish heap gave age of the artefacts. The next-oldest writing from the region is on a monument at a site of the Zapotec culture 300 kilometres to the west. But its date is poorly constrained, to sometime between 300 BC and 200 AD. Three later cultures in the same area used similar writing, the well-known Mayan, and the lesser-known Isthmain and Oxacan.

The cylinder shows two glyphs linked by lines to the mouth of a bird, giving the impression the glyphs are being spoken. One is "ajaw," meaning "king," and the other "three ajaw", a day in the sacred 260-day calendar used throughout the region for over a millennium.

Body paint

Later cultures used similar lines to show speech by people as well as by animals. When covered with ink or paint, the roller printed the bird and symbols on cloth or people's bodies. The date probably was the king's name, a common practice at the time.

"It's a kind of royal seal, used in decoration," Mary Pohl, an anthropologist at Florida State University in Tallahassee, told New Scientist. People in San Andres probably wore it "to show their fealty to the king" who resided at the main Olmec city of La Venta nearby.

The Olmec were the first American culture with a distinct ruling class, and Pohl believes they developed writing for rituals and rulers. Later Mesoamerican writing retained the links to kings and rituals, including the sacred calendar. Pohl says that writing could have originated at the start of the first Olmec culture in 1300 BC, but no evidence has survived.

In contrast, Old World writing is far older and traces back to tokens placed in clay envelopes to keep account of animals or other possessions. By about 3000 BC, symbols written on tablets replaced the tokens, becoming the world's first writing.

Journal reference: Science (vol 298, p 1984)