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Nabta: Circle in the Sand Glossary
Nabta: Circle in the Sand

To the people of ancient Nabta, in the desert of southern Egypt, the summer solstice meant life. Soon after the Sun reached the northernmost point in its annual trek across the sky, monsoons brought precious rainfall. Not much rain, mind you — no more than four to eight inches a year, about the equivalent of the annual rainfall in Las Vegas or Phoenix. But for a few weeks, water filled shallow desert basins. Grass grew along the banks, providing fodder for cattle, and wells filled with enough water to sustain small nomadic tribes for the entire year.

To help them predict and commemorate this life-giving event, the people at Nabta built an observatory — a 12-foot (4-meter) circle of flat stones, with four pairs of taller stones aligned opposite each other. Two pair provided a "window" on the solstice sunrise, while the other two aligned on an almost-perfect north-south axis.

Tall stones arranged in a circle may have served as a crude observatory at Nabta in the Egyptian desert.

Nabta's calendar circle was used at least 6,000 years ago, and probably earlier — at least a millennium before the first stones were laid at Stonehenge in England. Although Nabta's calendar circle is not nearly as grand, it has been nicknamed "the Egyptian Stonehenge."

Nabtans also erected megaliths — dark stones that towered up to 10 feet (three meters) above the desert landscape, scattered across a square mile. Some of the megaliths formed north-south and east-west sightlines, like a giant stone compass, and probably remained visible when the summer inundation filled the Nabta basin.

"We see two kinds of astronomy here — solstice alignments and cardinal alignments," says J. McKim Malville, a professor of astronomy at the University of Colorado at Boulder and a member of the team that confirmed the alignments in a paper published earlier this year. "The cardinal alignments are what you'd expect for people who travel across the desert with no particular way to guide them other than the stars. As they traveled, their tracks were obliterated, so they had to know north, south, east, and west.

"And the presence of lines pointing to the solstice indicates that they knew the summer rains would begin soon after — something that was vital to everyday life," Malville adds.

Nabta's calendar circle and megaliths illustrate the interconnectedness of astronomy, religion, and daily life that was common in most ancient cultures. Instead of an academic pursuit, astronomy was an integrated part of daily life. The Sun and stars helped the Nabtans plan for the rainy season and find their way through a hostile environment. In return, the Nabtans probably worshipped the heavens to some extent, or at least incorporated the Sun and stars into their rituals.

The Nabta story has two beginnings. The first took place about 11,000 years ago, when a climate change caused monsoonal rains to move north from central Africa into southern Egypt, well to the west of the Nile River. The second came in 1973, when a team of archaeologists stopped for a bathroom break during the vertebra-twisting drive from the Libyan border to the Nile Valley. The former brought life to the formerly barren dunes of the southeastern Sahara; the latter brought rebirth, as scientists discovered a site abandoned since the earliest days of Pharaonic Egypt.

"We were standing around, minding our own business, when we noticed potsherds and other artifacts," says Fred Wendorf, the Henderson-Morrison Professor of Prehistory at Southern Methodist University in Dallas, who has led the efforts to map and excavate Nabta. "We happened to be standing right on a site that was 9,000 years old."

The artifacts were inside a kidney-shaped basin, known as a playa, about six miles (10 kilometers) long by four miles (seven km) wide. Bedouin workers named the site Nabta, which means "little bushes," for a few dried plants found at the otherwise lifeless site.

Wendorf returned to Nabta several times during the 1970s. He found that the first humans appeared at Nabta between 10,000 and 10,500 years ago. These small nomadic bands brought their domesticated cattle to the shallow lakes after summer rains, but moved away again when the water evaporated.

Around 9,000 years ago, they began to inhabit the area year-round, digging deep wells, harvesting wild foods, making their own pottery, and building settlements with as many as 50 houses (though not all of them were occupied at the same time). But fickle winds pushed the monsoons away twice over the next 2,000 years, so people moved in and out of the region.

Finally, about 7,200 years ago, the rains returned, ushering in a lengthy period of stability and prosperity for Nabta. Wendorf says it's not clear how many people inhabited the region then. "We have sites with hundreds of hearths, but we don't know how many were in use at one time," he notes. "I have a feeling the number wasn't as big [as before]. But it took some people to build this place."

Surveys revealed 30 piles of stones scattered around the playa. Beneath one pile, researchers found a chamber containing the complete skeleton of a young adult cow. They then turned to a larger pile, which they hoped would contain the burial chamber of an important leader — a King Tut's tomb of the Sahara. "We were seeing sugarplums," says Wendorf. The site yielded a large statue that resembles a cow (although it could be a representation of a god or something else entirely) sitting atop a slab of carved bedrock, but no tomb.

During early expeditions to Nabta, Wendorf also noticed some large stones protruding from the sand, apparently at random. "We mapped these big outcrops of rock as bedrock," he says. "We weren't looking for anything else."

But in 1991, as Wendorf walked past one of the rocks, "I thought it looked strange." He found that the stone extended about five feet (1.5 meters) into the playa sediments, with another six feet of sediment beneath it. In all, it measured almost 10 feet tall, six feet wide, and two feet thick (3x2x0.7 meters). "It didn't float there — it was quarried about a half-mile away," Wendorf notes. Eventually, Wendorf's team dug trenches around nine other stones — two of them intact, the others broken and lying on their sides — with similar results.

"I also went a bit farther north, and a site I thought was a house was really a circle of small slabs, with four pair of larger stones set closer together," Wendorf recalls. "Right away, the association suggested it must be a crude calendar. I thought I better get an archaeoastronomer out here."

Malville joined Wendorf and two other researchers, Ali A. Mazar of the Egyptian Geological Survey and Romauld Schild of the Polish Academy of Sciences in Warsaw, on an expedition in 1997. Malville, who splits his time between archaeoastronomy and astrophysics, has studied possible astronomical sites in India and the American southwest.

At Nabta, team members used a constellation of satellites that can pinpoint any location on Earth to within a few inches to draw highly accurate maps of the site. They also used surveying instruments to obtain true measurements of the cardinal directions.

"The astronomical nature of the site was clear while we were there," says Malville. "These alignments are so simple and straightforward, there's no doubt about them."

Quick calculations confirmed that the rising Sun would have appeared between two sets of stones in the calendar circle on the date of the June solstice about 6,000 years ago. The other pair align just two degrees from a true north-south axis, which isn't bad considering that at the time, no star marked the north celestial pole. (Earth's polar axis points to different locations on the sky over a 26,000-year cycle.)

Both Malville and Wendorf say that the calendar circle probably served a ceremonial or ritual purpose; the small discrepancies in its alignments suggest that it was not a measuring device.

Malville says the Nabtans might also have paid special attention to the solstice Sun because the site lies near the Tropic of Cancer, which marks the Sun's northernmost point. About three weeks before and three weeks after the solstice, the noontime Sun would have appeared at the zenith — the point directly overhead. Vertical columns, like the megaliths or the sighting stones in the calendar circle, would cast no shadows as the Sun passed through the zenith — a moment that had great symbolic importance to many early cultures.

"The standing megaliths would have been apt devices to acknowledge the zenith Sun near the onset of the rainy season," the researchers write in the April 2 issue of Nature. "Placed in playa deposits, the megaliths would have been partly submerged in the rising waters of the summer monsoon, and they may have been considered to be ritual markers of the onset of the rainy season."

Two megaliths form a north-south line, while three others are aligned east-west. Almost a score of other megaliths appear to form four other sightlines. Malville and Wendorf say these alignments may have pointed to important stars or constellations, although they won't reveal more details until after publication of a second paper later this year. "We have some really interesting new developments, but we're very cautious," says Malville.

The researchers are glad to discuss the possible significance of the Nabta site, though.

"I think it was a regional ceremonial center," says Wendorf. "During the rest of the year, people were widely scattered. But once a year, they gathered at this big playa. We have these megaliths, the calendar circle, the cow burials, which are not found at other places. This may have been a meeting ground between these people and the people living in the Nile Valley."

In fact, the Nabta culture may have spurred the development of the kingdom of Egypt, which rose to prominence about 5,000 years ago. Although the people of the Nile raised few cattle, their early religion incorporated cattle worship, Wendorf notes, suggesting a connection to the cattle-raising Nabtans.

Regardless of what happened in the Nile Valley, wind patterns in the Sahara once again shifted about 4,800 years ago, and the monsoons moved southward. Nabta's lakes evaporated, the wells dried up, and the land become uninhabitable. The culture of Nabta disappeared. The summer solstice no longer brought life; it was simply another hot, sunny day in the unforgiving Sahara.

by Damond Benningfield, executive editor of StarDate magazine and writer of StarDate: Ancient Horizons.