The discovery of carvings on a snake-shaped rock along with 70,000-year-old spearheads nearby has dramatically pushed back the earliest evidence for ritual behavior, or what could be called religion. The finding, which researchers have yet to formally publish, comes from a cave hidden in the Tsodilo Hills of Botswana, a mecca of sorts for the local people, who call it the Mountain of the Gods.

"It's very big news," says Sheila Coulson, an archaeologist at the University of Oslo in Norway and leader of the study. Prior to the discovery, researchers had identified signs of ritual practice going back at most 40,000 years from sites in Europe.

Researchers believe that anatomically modern humans emerged from East Africa perhaps 120,000 years ago. "The difficulty was always this incredible time lag between that occurrence and any more complex aspect of the culture other than just basic survival," Coulson says. Although some carved ornaments and wall markings from another African site are as old as the new find, they seem to have had no obvious ritual significance.

A chief of the local San people invited Coulson and her colleagues to study the cave in Tsodilo Hills. They were unprepared for what they found when they entered: a six-meter-long rock that bore a striking resemblance to a snake, including a mouthlike gash at the end. "My first words I remember saying are, 'My god what is that?'" Coulson says. "I'd never seen anything like it."

Hundreds of small notches, widely spaced in some places and closer together in others, covered the rock. Entrants to the cave apparently made these markings to enhance the snake illusion by creating the impression of scales and movement [see picture below]. "When flickering light hits it, it very much looks like the snake is flexing," Coulson says. Snakes feature prominently in the traditions and the mythology of the San, sometimes called the Bushmen.

Although many of the carvings looked old, more reliable markers of the site's longevity lay buried in rock half a meter beneath the soft cave floor. In a one-meter-wide, two-meter-deep excavation right next to the snake, the researchers uncovered more than 100 multicolored spear points from a total of 13,000 man-made artifacts.

The tips closely resemble those found elsewhere in Africa that researchers have dated at up to 77,000 years old, Coulson says. Judging from the rare colors of the stone points and the pattern of fragments, people from far and wide likely brought them to the cave partially made and finished working them there, she explains.

Some of the stone tips seem to have been burned or smashed in what may have been a type of sacrifice. Of 22 tips made from red stone, all of them show cracks and faults consistent with exposure to high heat, Coulson says, and some were burned white. Other spearheads exhibit chips and marks that suggest someone had struck the finished tips dead-on, something that researchers have observed at sites in Siberia, she notes.

"You put it all together and clearly something very extraordinary is happening," says archaeologist and prehistoric religion specialist Neil Price, also at the University of Oslo, who was not part of the dig. "You have things occurring over a long period of time that do not have a functional explanation. There must be a whole complex of thinking behind these actions, and that in itself is exciting."