PlanetQuest: The History of Astronomy
Nabta Playa is a natural depression with an area of about 5000 square kilometers
(2000 square miles) located west of the Nile River in what is today southern
Egypt. Until roughly 11,000 years ago, the wide plains of Nabta Playa were too
dry to support permanent human settlement. But by then, weather patterns began
to shift and scientists think that summer monsoons of Central Africa began to
reach into the area, creating large temporary lakes or playas.
Scientists have hypothesized that over time these lakes encouraged increasingly
complex human societies to form. Evidence points to early transhuman cattle
pastoralism (meaning humans migrated with their animals every year), as well
as the elaboration of religious beliefs and cultural practices. But beginning
about 9000 years ago, larger permanent settlements developed that relied
on wells in addition to sheep, cattle, and goat herding. After a period of intense
drought between 8000 and 7000 years ago, the climate again shifted to support permanent
settlement in the playa, and scientists believe these groups developed a sophisticated
society centered on religious beliefs. Most importantly, it appears that by
about 6500 years ago, inhabitants at Nabta Playa developed a sophisticated, accurate
way of marking time and seasons, using the stars as their guides. About 4800 years ago,
another climate change occurred, and today scientists believe that the Nabta inhabitants
may have gradually made their way into the more fertile Nile River Valley—but no one knows for sure. Are these people the ancestors of ancient Egypt?
Maybe, but much more research is required.
Nabta Playa is currently the oldest known
archaeoastronomy site in the world, older than Stonehenge by at least 1000 years.
There are five known alignments of megaliths stretching out from a group of
central megalithic structures at the settlement. When archaeoastronomers began
to draw lines along the alignments, they realized that the lines very closely
matched the direction of sunrise on the summer
solstice, as well as the rising points of Sirius, Dubhe, and Orion's Belt.
In addition, vertical stones—which would cast no shadow when the Sun passes
directly overhead—marked the sun's zenith
passage, which happens each year about three weeks before and three weeks
after the solstice, and may have signaled the onset of the summer monsoons.
Scientists also found several strong north-south and east-west alignments that
might have helped Nabtians navigate and track stellar movements.
Why are megaliths important to us today? Well, building a megalith isn’t
easy. And building a megalith that actually accurately measures the movement of stars
across seasons is even harder. Think of it: first you have to know a lot of
people to help you move some very large rocks. Each megalith at Nabta Playa
is about 2 m (6 feet) wide by 3 m (9 feet) high. Then you have to convince your
friends that moving a large slab is worthwhile. The megaliths at Nabta Playa
probably came from a quarry at least 0.5 km (0.3 mile) away from where Nabtians
finally placed them. That's quite an effort. And then you have to carefully
watch the sky and track stars as they move across the sky over the years, so
that the megaliths can be properly aligned. Finally, the Nabta megalith slabs
are actually carved, which might have shown certain stellar alignments based
on the shape of the stone. So the complexities of building a megalith
can tell us quite a bit about the society that built it.
Because building the megaliths at Nabta Playa took significant organization
and skills, scientists think that the Nabtians had, by about 6500 years ago, developed
a fairly advanced society. They could organize labor to move the slabs, build
a number of houses, dig wells, and perhaps even specialize in certain kinds
of tasks, sharing the burdens of everyday life. The sophistication and accuracy
of the megaliths themselves, along with evidence of cattle worship that anthropologists
and archaeologists recently discovered, also tell us that this society probably
developed in complexity over time.
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Holocene Settlement of the Egyptian Sahara: The Archaeology of Nabta
Playa, Fred Wendorf, Romuald Schild, Kit Nelson, eds., Kluwer
Academic/Plenum Publishers, New York, 2001.
Malville, J. McKim, et al., "Megaliths and Neolithic Astronomy in Southern Egypt," Nature, April 2, 1998.
State University emuseum
NASA Ancient Observatories
Methodist University Anthropology Department
of Colorado at Boulder