In aboriginal lore, some sandstone outcroppings in northwest Australia mark the spot where a spirit called Jinmium, attempting to flee her pursuer, turned herself into stone. Jinmium is also the site, archeologists reported last year, of the world’s earliest known art. Carved into the face of a 13-foot-tall sandstone monolith, and into many surrounding boulders, are thousands of shallow circular depressions, typically an inch across and half as deep. The marks were made at least 60,000 years ago--that’s twice as old as any European cave painting.
Richard Fullagar, an archeologist at the Australian Museum in Sydney, first came upon the site in 1992, while surveying the area with his wife, geologist Leslie Head, but at that time he didn’t know how old it was. I was stunned by the density of these things, he says. There are rocks the size of a Volkswagen that are totally pecked with these markings. The marks were apparently made with pieces of quartz about the size of a tennis ball, which Fullagar has also found at the site. He estimates that each mark took a half hour to an hour to make. That means many thousands of Homo-hours went into creating the oeuvre at Jinmium.
The site’s significance remains mysterious. Though simple in form, the marks seem to be part of some larger, more complex system that extends over about 62 acres. Boulders covered with the gouges form parallel lines or arcs stretching hundreds of yards, connecting different rock shelters, or converging on a rock tunnel just big enough for a person to squeeze through. Fullagar has also found a similar site some 20 miles north, called Granyilpi. Curiously, says Fullagar, in aboriginal mythology the spirit Jinmium began her journey at Granyilpi and ended it at Jinmium.There is nothing in aboriginal lore, though, about the origin or significance of the marks.
When Fullagar began excavating around the base of the tall sandstone monolith, he found that the marks on its surface continued down about three feet underground. He also found stone tools, apparently older than the markings, in deeper sediment layers around the monolith. Fullagar had some of the sediments dated through thermoluminescence, a technique for determing how long ago quartz grains were buried and began accumulating energy released by radioactive elements. The results astonished him. The lowest--and presumably oldest--marks on the monolith appear to be about 60,000 years old, judging from the age of the sediments that buried them. The stone tools don’t have an exact date, but were found below sediments that are 116,000 years old.
Fullagar’s discovery pushes back the date of colonization of Australia--traditionally placed at 60,000 years ago--to perhaps more than 116,000 years ago. That was just about when modern humans supposedly emerged from Africa, according to the latest genetic evidence. If Fullagar’s dates are right, the Africans must have crossed Asia and reached Australia very quickly indeed. Or else molecular biologists don’t have the departure date right.