Image: UNIVERSITY OF COLORADO
The site, near Nabta in the Nubian desert, was discovered several years ago by a team led by Southern Methodist University anthropology professor Fred Wendorf. It consists of a small stone circle, a series of flat, tomb-like stone structures (containing the bones of cattle) and five lines of standing and toppled megaliths. The stone slabs, some of which are nine feet-high, were dragged to the site from an exposed outcrop of sandstone a mile or more away from the site. Each is embedded in the soil on top of a shaped table rock Last year, archaeoastronomer J. McKim Malville of the Department of Astrophysical and Planetary Sciences at the University of Colorado and his colleagues conducted a survey using a global positioning satellite that confirms the stones' alignment north-south, east-west and to the summer solstice sun as it would have been seen 6,000 years ago.. The scientists reported their results in the April 2, 1998 issue of Nature.
When the stones were erected, the area received enough rain in the summer monsoon for temporary lakes, called playa, to form. The site, built on the shore of one such lake. Radiocarbon dating indicates that Neolithic herders began coming to Nabta about 10,000 years ago. It was used periodically by nomads until about 4,800 years ago, when the monsoon moved southwest and the area again became arid.
Image: UNIVERSITY OF COLORADO
At the height of its human occupation--about 6,000 years ago--Nabta supported well-established communities. One village consisted of 18 houses served by deep wells. Beneath the surface slabs of the largest megalithic structure was a sculptured rock resembling a standing cow. The team also excavated several cattle burials at Nabta, including an articulated skeleton buried in a roofed, clay-lined chamber. The late Neolithic occupants apparently used cattle in their rituals just as the African Massai do today, says Malville.
There is much domestic debris on the site, including small, fire-blackened hearths, the bones of gazelles, hares and other animals, fragments of pottery and carved and decorated ostrich eggshells. However, no signs of human burials or remains have been found at Nabta. "The nomadic groups must have engaged in a variety of activities during summer occupation, such as social bonding, marriage, trade and ritual," the authors note.
The small stone circle, just 12 feet in diameter, consists of four sets of upright slabs, which could have been used for sighting along the horizon. Two sets were aligned in a north-south direction while the second pair of slabs provides a line of sight toward the summer solstice horizon. The centerline of one slot between the slabs would have picked up the first gleam of the rising sun at the summer solstice. Because Nabta is close to the Tropic of Cancer, the noon sun is at its zenith on two days, about three weeks before and three weeks after the summer solstice. On these days, upright objects do not cast shadows--something the authors believe was significant to ancient people.
The researchers also identified an east-west alignment between one megalithic structure and two stone megaliths about a mile distant. There are also two other geometric lines, involving about a dozen additional stone monuments that lead both northeast and southeast from the same megalith. Individual stone monoliths would have been partially submerged in the lake as water level varied during spring and fall, and so they may have been ritual markers for the onset of the rainy season. "The organization of the megaliths suggests a symbolic geometry that integrated death, water, and the sun," the authors said.
One of the earliest pyramids, the step pyramid at Saqqara, was built 500 years after the changing climate rendered Nabta uninhabitable. It may have incorporated astronomical features known to the ancient Nubians. The authors speculate that the development of the monumental buildings of ancient Egyptian civilization was hastened by the arrival in the Nile valley of well-organized nomadic groups with a sophisticated cosmology.