Astronomy of Nabta Playa African Skies July 2007 No.11から
J. McK Malville 1, R. Schild 2, F. Wendorf 3 and R. Brenmer 4
1Department of Astrophysical and Planetary Sciences, University of Colorado, USA
2Institute of Archaeology and Ethnology, Polish Academy of Science, Warsaw, Poland
3Department of Anthropology, Southern Methodist University, Dallas, USA
4Aldwick, West Sussex, U.K.
e-mail: 1Kim.Malville@colorado.edu
Abstract.
The repetitive orientation of megaliths, human burials, and cattle burials toward the northern regions of the sky reveals a very early symbolic connection to the heavens at Nabta Playa, Egypt. The groups of shaped stones facing north may have represented spirits of individuals who died on the trail or locally. A second piece of evidence for astronomy at Nabta Playa is the stone circle with its two sightlines toward the north and toward the rising sun at the June solstice. Finally, the five alignments of megaliths, which were oriented to bright stars in the fifth millennium, suggest an even more careful attention to the heavens. The “empty tombs” and deeply buried table rocks of the Complex Structures provide some of the greatest enigmas of Nabta Playa. The recurrent symbolism of the ceremonial centre involves issues that would have been of both practical and symbolic importance to the nomads: death, water, cattle, sun, and stars.
Introduction
The southwestern desert of Egypt, now one of the driest areas on Earth, was not always so inhospitable. Beginning about 9000 BC the summer monsoon rains moved northward from central Africa and created a landscape where nomadic pastoralists with their cattle could survive.11,12,13,14 Even with rains it was still a dry environment with an annual rainfall of no more than 100–150 mm. Rain was unpredictable, and the climate was punctuated by numerous droughts, some of which caused the desert to be abandoned for long periods of time. Game was scarce, consisting of small gazelles and hares. Cattle were walking larders of milk, blood, and meat, used in a manner similar to those of modern Masai in Kenya. Cattle allowed people to live in the desert, thereby controlling their lives and dominating much of their ceremonialism.
Located 100 km west of Abu Simbel, Nabta Playa is a large internally drained basin (Figure 1). During the early Holocene (ca 9000–3500 BC), the playa was occasionally flooded, attracting nomads to settle intermittently on its shores. The first settlements at Nabta were small seasonal camps of cattleherding and ceramic-using people. These people probably came into the desert after the summer rains from either farther south or the adjacent Nile in search of pasture for their cattle. Each autumn, when the water in the playas dried up, they had to return to the Nile or to better-watered areas in the south.
By 7000 BC the settlements became larger, and their inhabitants were able
to live in the desert throughout the year by digging large, deep wells.
They lived in organised villages consisting of small huts arranged in straight
lines. By 6800 BC they began to make local pottery. A few hundred years
later, around 6100 BC, sheep and goats appear for the first time, almost
certainly introduced from southwest Asia.
Ceremonial Centre at Nabta Playa
Nabta probably began to function as a regional ceremonial centre during
the Middle Neolithic period (ca 6100– 5600 BC) during the summer wet season,
when the playa had reached its largest size. By a regional ceremonial centre,
we mean a place where related but geographically separated people gather
periodically to conduct ceremonies and to reaffirm their social and political
identity. These gatherings occurred along a dune on the northwestern shore
of the playa where there are hundreds of hearths, extensive cultural debris,
and many cattle bones. While present at most other sites, bones of cattle
are elsewhere never very numerous, which is good evidence that they were
kept primarily for their milk and blood, rather than for meat. This pattern
resembles the role of cattle among modern African pastoralists, for whom
cattle represent wealth and political power. They are rarely killed other
than on important ceremonial or social occasions such as the death of a
leader or a marriage.
Following a major drought, which drove earlier groups from the desert,
the Late Neolithic began around 5500 BC with a new group that had a complex
social system expressed in a degree of organisation and control not previously
seen. These new people, the Ru’at El Baquar people (the Cattle Herders),
were responsible for cattle burials in clay-lined and roofed chambers covered
by rough stone tumuli.
The Valley of Sacrifices and the Cromlech
Along the western rocky bank of a wadi entering Nabta Playa from the north, which we have called the Valley of Sacrifices, there are about ten identifiable tumuli. Built of broken sandstone blocks, the tumuli contained offerings of parts of butchered cattle, goats and sheep. The largest and perhaps the oldest tumulus contained an entire young cow, the most precious offering that a pastoralist can make. A piece of tamarisk from its roof yielded a radiocarbon date of 5270 + 270 years BC. Probably a female just entering adulthood, the animal was lying on its left side, oriented approximately northsouth, with its head in the south. This wadi brought water to the playa and would have been an appropriate spot to ask the gods for rain by performing cattle sacrifices.
The wadi ends in a small cromlech or stone circle, on top of a small sandy knoll1,10 (Figures 2, 3, 4). The circle, approximately 4 m across, contains sets of upright, narrow slabs aiming the eye approximately to the north and to the position of the rising sun at the summer solstice, which would have been near the start of the rainy season. A radiocarbon date from a hearth adjacent to the cromlech yielded a date of 4800 + 60 years BC. The centre of the cromlech contains six upright slabs arranged in two lines, for which the astronomical functions, if any, are not clear. One of our Bedouin workers reported that it was not uncommon in the desert to set similar stones in the sand and use their moving shadows as time keepers. Another well-known stone circle was discovered by Bagnold2 in the Libyan desert. It is larger (8.5 m) but seems to be made up of the same kind of thin stone slabs as at Nabta. No evidence of astronomical orientations has been reported, and none is readily discernable in photographs of the circle.
The Complex Structures
To the south of the Valley of Sacrifices is a series of knolls carved in the ancient lake clays by the desert winds. The area contains about 30 complex megalithic structures built during the Terminal Neolithic by Bunat El Ansalm people or Megalith Builders. The Terminal Neolithic at Nabta Playa extended from 4600 BC to the abandonment of the area in approximately 3400 BC. The complex structures or tumuli were set in silt deposited during the final part of the Middle Neolithic.
Some of the stones on the top of these complex structures are standing upright, typically arranged in an oval with a larger recumbent stones in the centre. The ovals are 5–7 m long and 4–6 m wide, oriented north-south or rotated slightly to the west of north. The recumbent stones have a similar orientation.
The largest of the complex structures, A, appears to play a major role in the symbolism that becomes manifest in the ceremonial centre during the Final Neolithic.13 We originally thought the structure might contain elite graves, but excavation has failed to disclose any human remains. Very significantly, it is the focus of the five radiating megalithic alignments. The builders of Complex Structure A dug a pit through playa sediments to expose a table rock at a depth of 2.6 m (Figure 5). The rock is a thick lens of hard, quartzitic sandstone that remained after the surrounding softer sediments had been removed by erosion. A similar rock was found in the second complex structure that was excavated, and in a third structure another table rock was located by a probe. The table rocks were probably formed during the initial deflation of the Nabta basin by wind, long before the deposition of the playa sediments. In the case of Complex Structure A, the northern side was flattened to the east-west and the western side was rounded. Its top appears to have been worked and smoothed. After shaping the oval rock measured 3.3 m by 2.3 m with its long axis aligned north-south.
How or why the buried table rocks were chosen remains a puzzle. It seems unlikely that the rocks had been found accidentally during excavation for wells, as these were in dunes at the edge of the playa and not in the playa sediments. It is conceivable that these round, large quartzitic lenses were part of the symbolic landscape of the Middle Neolithic and became significant before the establishment of the complex ceremonial centre. Perhaps their locations had been marked by rock cairns before gradual burial by playa sediments.
The pit was partially refilled and a large secondary stone, weighing 2–3 tons was placed over the centre of the table rock (Figure 6). This secondary stone was also carefully shaped with a large head-like projection facing slightly west of north. It was held upright by two large slabs set against the structure at its north end. One side had clearly been smoothed by pecking. The stone has a vague resemblance to a cow and may have represented a surrogate sacrificial cow.
Alignments
After reanalysis of our previous measurements and a new campaign of mapping the sandstone blocks of the area, we identified five alignments of megaliths that radiated outward from Complex Structure A. Many of the megaliths, if not all, are sculptured with anthropomorphic shoulders suggesting that they served as stele, perhaps representing the dead (Figures 7, 8, 9).
Dates for the quarrying and placement of these stones in the sediments of the playa are based on radiocarbon dates from the nearby quarry. Five radiocarbon dates from the quarry are 4500BC to 4200 BC. Not all the blocks that had been quarried were used, as approximately 100 m east of the quarry is a storage area where dozens of additional sandstone blocks have been stored. Since we also have a carbon date of 3600 BC for Complex Structure E , we estimate that the megalith period lasted for approximately 800–900 years from 4500 BC to 3600 BC.
Our original measurements of the locations of the megaliths9,10 have been complemented by satellite imagery by the Quickbird satellite and additional GPS measurements by Brophy and Rosen5. We are gratified that there is good agreement on the locations of the megaliths by these independent measurements. In our analysis we combine the two sets of GPS data and the satellite results (Figure 10).
For our calculations of precession, we have used the formulae of Bretegon et al.3 and have included the effects of refraction and extinction. Because of the movement of the dunes over 6–7 millennia, it is difficult to estimate the actual horizon, and we assume a level physical horizon. Many of the stele are scattered and fragmented, and in estimating the dates when these alignments may have been oriented to certain stars, we include an uncertainty of + 0.6°. This uncertainty is meant to include not only the effect of fragmentation, but also the inherent irregularities of the locations of the stele as we suspect high precision in orientation may not have been a high priority.
While we had originally considered Dubhe, the brightest star in Ursa Major, to be a possible candidate for the three northernmost alignments, Arcturus now appears to be a much more likely choice during the period of megaliths (4 600–3 600 BC). It is the brightest star in the northern celestial hemisphere and the fourth brightest star in the night skies. There are three occasions when alignments A1, A2 and A3 were oriented to the rising positions of Arcturus in the period of the megaliths. Each of these three alignments may have been built to account for the changing location of that star due to precession.
The alignment, B2, may have been lined up with Alnilam, one of the three stars in the belt of Orion between approximately 4300–4100 BC, with winter solstice sunrise and later with Sirius, near the end of the Terminal Neolithic. The set of stele, B1, would have lined up with Sirius and α Centauri which is the third brightest star in the night sky, in the period 4600–4300 BC. A closer inspection of the southernmost alignment, which we had initially designated as C, indicates that it consists of stones resting on the sides and tops of dunes and may not represent an original set of aligned stele; we refrain from interpreting that alignment.
With the exception of Canopus, these alignments may have been associated with the brightest stars in the night sky of Nabta. In 4500 BC, Canopus would have risen with an azimuth of 159°and would have reached a maximum altitude of approximately 8°above the southern horizon. It is conceivable that the slight rotation of some of the megalithic slabs away from north-south was due to an attempted alignment with the rising position of that star.
The two major periods of alignments appear to be 4600–4200 BC, which would encompass Sirius, two orientations toward Arcturus, α Centauri, and the Belt of Orion. The second window at 3800–3400 BC, which would have included Sirius and Arcturus, may reveal a resurgence of interest in the heavens just as life was getting increasingly difficult in the desert. There are some interesting geometrical aspects of the alignments which may have been important for the Megalith Builders. In their navigation across the desert, nomads would have paid attention to cardinal directions and right angles. Two sets of megaliths, A3/B2 and A1/B1 differ by approximately 90°and connected Sirius with the brightest star in the northern sky. During the second window of time at approximately 3820 BC Arcturus rose 30.35°east of north. which was also the angular distance of the star from thezenith. With a declination of 52.85°,at its upper culmination Arcturus reached 30.35°from the zenith.
In their analysis of the positions of the alignments, Brophy and Rosen5
propose that the southernmost alignment, C, was associated with Sirius
in 6088 BC and that the other alignments were associated with Vega and
stars of Orion in 6270 BC. Their suggested dates are about 1500 years earlier
than our best estimates for the Terminal Neolithic and the construction
of megalithic structures by the Bunat El Ansalm people. Brophy4 has also
suggested that the table rock of Complex Structure A is a map of the Milky
Way galaxy dating from 17500 BC showing spiral arms and a neighbouring
dwarf galaxy. He proposes that the stones of the cromlech represent maps
of the stars of Orion as early as 16500 BC. These extremely early dates
as well as the proposition that the nomads had contact with extra-galactic
aliens are inconsistent with the archaeological record. Inference in archaeoastronomy
must always be guided and informed by archaeology, especially when substantial
field work has been performed in the region.
Fields of Stele
In addition to the alignments, there are clusters of smaller sandstone blocks, ranging in weight from several tons to less than 50 kg.110 A few are upright, and others with broken bases embedded in the clays suggest that originally the stele had been set up vertically, facing north. The dynamics of collapse involved the prevailing northerly winds that carved holes in front of the megaliths and caused their collapse. These depressions can be found underneath the northern faces of the collapsed blocks. Many are sculptured in a manner similar to the blocks of the alignments, with anthropomorphic shoulders suggesting that they too served as stele, representing the dead. Groups of stele may represent departed members of specific clans or extended families.
Prehistoric Herdsmen
Judging from the elaborate burials at the nearby cemetery at Gebel Ramlah about 20 km from Nabta Playa, the nomads associated with the ceremonial centre were prosperous and healthy, possessing a strong aesthetic sense and interested in preserving and honouring their dead.7,6,8 Since it is a rare opportunity to learn about people associated with such an early ceremonial centre, it seems worthwhile describing these prehistoric herdsmen in some detail. The cemetery contained 67 individuals in both primary and secondary inhumations. The most reliable carbon date is from bone collagen giving us 4360 BC + 60 years. Inspection of dental features indicates that two different populations, Mediterranean and sub-Saharan, were represented in the cemetery. The lack of differences in burial goods indicates there was little, if any, social stratification in the community.
The exceptional wealth of grave goods is notable. Many were buried with ceramic pots, some of which were elaborately decorated. Vessels known as tulip beakers were apparently produced exclusively as grave goods and usually placed on the chest or near the head. They were also accompanied by sets of cosmetic artifacts consisting of stone pallets, stones for grinding colour-bearing minerals, and containers made of ivory, bovine horn, stone or ceramic. Many of the graves contained large sheets of mica, more than 10 cm across and 1 cm thick. One slab was shaped in the form of a tilapia, a fish frequently encountered in the Nile. This is the oldest known sculpture to be discovered in Egypt.
The lack of dental enamel hyperplasia, an indicator of growth disruption during early childhood, also indicates that children must have been healthy and well-fed. The tall stature of the burials suggests good health and nutrition. Secondary inhumations may have been of individuals who died while travelling. All seven primary inhumations were in flexed positions, head oriented to west, facing south.
The cemeteries indicate that there was a keen interest in preserving the remains of the dead. There were two skulls in which some of the upper teeth were replanted in the lower jaw and vice versa. The forearm of one woman was found with four bracelets which had been fastened to the skeleton after death. Many of the burials were sprinkled with large amounts of red hematite dust which, in numerous cultures, is associated with blood, the life force, and high status.
An important conclusion we can draw from these burials is that the people living near or visiting the playas of Gebel Ramlah and Nabta participated in a wide trading network, which could bring them into contact with ideas as well as trade goods. Their contacts stretched far as evidenced by turquoise from the Sinai Peninsula, shells from the Nile, mica from mountains along the sea coast and ivory from elephants.
Each of the three cemeteries contains the graves of individuals who seem to have belonged to single clans. The individual graves that preserved anatomical order were of people who died at the settlement and were interred there. The secondary graves can be interpreted as burials of high status individuals who died during the distant migrations of the herders. It must have been important to bury them in the clan cemetery at a site that was believed to be the “centre place” for the culture.
Summary and Conclusion
The evidence for astronomical observations by these ancient herdsmen comes in three forms. The repetitive orientation of megaliths, stele, human burials and cattle burials toward the northern regions of the sky reveals a very early symbolic connection to the north. The apparent emphasis on death in the area suggests that the ceremonial centre may have functioned as a necropolis; the tumuli may have held stone cenotaphs or may have been cenotaphs (“empty tombs”) themselves. The groups of shaped stele facing north may have represented spirits of individuals who died on the trail or locally. The second bit of evidence for astronomy is found in the cromlech with its two sightlines toward the north and toward the rising sun at the June solstice. Finally, the alignments of stele, which were oriented to bright stars in the fifth millennium, suggest an even more careful attention to the heavens.
Interest in the northern part of the heavens does indeed seem pervasive
during the Late and Terminal Neolithic at Nabta Playa and Gebel Ramlah.
The northern circumpolar regionof the sky is that realm where stars never
set, and, later in dynastic Egypt, it became identified as the realm of
eternal life. Survival in the desert must have required an ability to navigate
by the stars as the nomads moved across the sea of sand without trails
or major landmarks. There was no bright star at the north celestial pole
at that time but north could have been inferred from the circulation of
stars around that region in the sky. On a flat northern horizon, the positions
of the rising and setting of bright stars could have been marked by cairns
and the midway position would have been north. North could also have been
established during the day by shadow-casting of a vertical stick or gnomon.
The “empty tombs” of the Complex Structures provide the greatest enigmas
of Nabta Playa. How or why the buried table rocks were chosen remains a
puzzle. It seems unlikely that the rocks had been found accidentally during
excavation for wells, as these were in dunes at the edge of the playa and
not in the playa sediments. It is conceivable that these round, large quartzitic
lenses were part of the symbolic landscape of the Middle Neolithic and
became significant before the establishment of the complex ceremonial centre.
Perhaps their locations had been marked by rock cairns before gradual burial
by playa sediments. Regardless of how they were initially located, the
buried table rocks underneath the megalithic slabs apparently became manifestations
of the sacred for the nomads. The symbolism embedded in the archaeological
record at Nabta Playa in the Fifth Millennium BC is very basic, focussed
on issues of major practical importance to the nomads: cattle,water, death,
earth, sun and stars.
References
1. Applegate, Alex. 2001. “Site E-92-9: A Possible Late Neolithic Solar Calendar.” In Holocene Settlement of the Egyptian Sahara: The Archaeology of Nabta Playa. Kluwer Academic, New York, pp. 463–467.
2. Bagnold, R.A. 1931. “Journeys in the Libyan Desert 1929 and 1930.” The Georgaphical Journal, Vol. LXXVIII No. 1.
3. Bretagon P., Rocher, P. and Simon, J.L., 1997. “Theory of the Rotation of the Earth.” Astronomomy and Astrophysics 319: 305–317.
4. Brophy, Thomas G. 2002. The Origin Map: Discovery of a Prehistoric, Megalithic, Astrophysical Map and Sculpture of the Universe. Writers Club Press, New York.
5. Brophy, Thomas G. and Rosen, Paul A., 2005. “Satellite Imagery Measure of the Astronomically Aligned Megaliths at Nabta Playa.” Mediterranean Archaeology and Archaeometry 5: 15–24.
6. Irish, J. D., Kobusiewicz, M., Schild, R. and Wendorf, F., 2003. “Neolithic Tooth Replacement in Two Secondary Burials from Southern Egypt,” Journal of Archaeological Science 30:281–85.
7. Irish, J.D., Schild, R., Froment, A. and Wendorf, F., 2002. “The Role of Neolithic Peoples in Northeast African Prehistory: A Biocultural Perspective from Nabta Playa, Egypt,” American Journal of Physical Anthropololgy. Supplement 34: 88–89.
8. Kobusiewicz, Michael and Schild, Romuald, . 2005. “Prehistoric Herdsmen.” Academia- The Magazine of the Polish Academy of Sciences. No.3 (7) 20–23.
9. Wendorf, Fred and Malville, J.M. 2001. “The Megalithic Alignments.” In Holocene Settlement of the Egyptian Sahara, Volume 1, The Archaeology of Nabta Playa. New York: Kluwer Academic/Plenum Publishers, pp. 489–502.
10. Malville, J.M., Wendorf, Fred, Mazar, Ali A. and Schild, Romauld,. 1998. “Megaliths and Neolithic Astronomy in Southern Egypt.” Nature 392: 488–490.
11. Schild, Romuald and Wendorf, Fred, 2004. “The Megaliths of Nabta Playa.” Academia- The Magazine of the Polish Academy of Sciences. No. 1 (1) 10–15.
12. Wendorf, Fred, Close, A.E. and Schild, R. 1992–1993. “Megaliths in the Egyptian Sahara.” Sahara 5:7–16.
13. Wendorf, Fred and Krolik, Halena, 2001. “Site E-96-1: The Complex Structure or Shrines. In Holocene Settlement of the Egyption Sahara, Kluwer Academic/Plenum Publishers: New York, pp. 503–520.
13. Wendorf, Fred and Schild, Romuald, 1998. “Nabta Playa and Its Role in Northeastern African Prehistory.” Journal of Anthropological Archaeology 17: 97–123.
14. Wendorf, Fred, Schild, Romuald and Associates. 2001. Holo- . cene Settlement of the Egyptian Sahara, Kluwer Academic/ Plenum Publishers: New York.
Fig. 2. Cross-section of the calendar circle mound cromlech.(Profile
by R. Schild)
Fig. 3. Reconstruction of the calendar circle cromlech.(Applegate 2001)
Fig. 4. Calendar circle cromlech.(Photograph by J. Malville)
Fig.5
Fig6～9
