Tim Radford
Stone Age people built the first astronomical observatory centuries before anyone had thought they did. Scientists working in the Sahara have identified a series of megaliths that predate Stonehenge in Britain and other sites by more than 1 000 years.
Around 6 500 years ago, an unknown people living in Nabta, southern Egypt, began dragging slabs of stone, nearly 3m high, into position on the west bank of the Nile.
The alignments run north-south and east- west, and point to the sun where astronomers estimate its solstice would have been 6 000 years ago.
“This is the oldest documented astronomical alignment of megaliths in the world,” says Professor McKim Malville of the University of Colorado at Boulder, who – with colleagues from the United States, Egypt and Poland – has completed a satellite survey of the stones. “A lot of effort went into the construction of a purely symbolic and ceremonial site.”
The ruins are beside what would have been the shoreline of a lake that filled with water about 11 000 years ago when the African monsoon moved north. It was used by nomads until 4 800 years ago, when the rainfall patterns shifted, and the area became arid and uninhabitable.
Five alignments radiate out from a central collection of stones. Beneath one was a carved rock resembling a cow standing upright.
The researchers report that they found the remains of several buried cattle, including a skeleton laid to rest in a clay-lined chamber. There were cinders from ancient hearths, and fragments of decorated ostrich eggs.
The stones are mute evidence of a vanished world -and a foretaste of the pyramid builders who would arrive 1 500 or 2 000 years later. Neolithic herdsmen came to Nabta, probably from further south in Africa, and used cattle in their rituals just as Masai tribesmen do today, says Malville. Because Nabta was close to the tropic of Cancer, the noon sun would be directly overhead and, for a brief while each day, the standing stones would cast no shadows.
“These vertical sighting stones correspond to the zenith sun during the summer solstice,” he says. “For many cultures in the tropics, the zenith sun has been a major event for millennia.”
Some of the other alignments are still puzzling the archaeoastronomers – scientists who specialise in interpreting patterns in stone left by vanished civilisations. Some of the monoliths would probably have been submerged in the lake and may have “marked” the onset of the rainy season. “The organisation of these objects suggest a symbolic geometry that integrated death, water and the sun,” says Malville.
The discovery points to a world peopled by nomadic herdsmen prepared to face daunting conditions.
The “high” culture of the Egyptians is traditionally thought to have been borrowed from Mesopotamia and Syria. But the forgotten stonemasons of Nabta clearly understood symbolism: Malville and his colleagues believe that they, rather than the Assyrians or the Babylonians, may have triggered the social complexity that ended in the pyramids of the Pha-raohs.