A publication of the Archaeological Institute of America
It was an odd sensation climbing over the Great Pyramid, looking for minute flecks of charcoal or other datable material, loaded down with cameras, scales, notebooks, and forms with entries for sample number, site, monument, area, feature, material (charcoal, reed, wood, etc.), matrix (gypsum mortar, mud brick, etc.), date, time, notes on details, extracted by, logged by, photograph numbers, and sketches. It was 1984 and the Edgar Cayce Foundation, named for an early twentieth-century psychic who claimed that the Sphinx and Khufu's Great Pyramid were built in 10,500 B.C., was paying for the analysis of our samples. Old friends and supporters of the deceased psychic had visited Giza in the early 1980s and several of them were willing to put their beliefs to the test by radiocarbon dating the Great Pyramid. Archaeologists believe it is the work of the Old Kingdom Dynasty 4 society that rose to prominence in the Nile Valley from ca. 3000 B.C. and built the Giza Pyramids in a span of 85 years between 2589 and 2504 B.C.
1984 Results. The 1984 radiocarbon dates from monuments spanning Dynasty 3 (Djoser) to late Dynasty 5 (Unas), averaged 374 years older than the Cambridge Ancient History dates of the kings with whom the pyramids are identified. In spite of this discrepancy, the radiocarbon dates confirmed that the Great Pyramid belonged to the historical era studied by Egyptologists. In dealing with the 374-year discrepancy, we had to consider the old wood problem. In 1984 we thought it was unlikely that the pyramid builders consistently used centuries-old Egyptian wood as fuel in preparing mortar. Ancient Egypt's population was compressed in the narrow confines of the Nile Valley with a tree cover, we assumed, that was sparse compared to less arid lands. We expected that by the pyramid age the Egyptians had been intensively exploiting wood for fuel for a long time and that old trees had been harvested long before. The 1984 results left us with too little data to conclude that the historical chronology of the Old Kingdom was in error by nearly 400 years, but we considered this at least a possibility. Alternatively, if our radiocarbon age estimations were in error for some reason, we had to assume that many other dates obtained from Egyptian materials were also suspect. This prompted a second, larger study.
The 1995 Project. During 1995 samples were collected from the Dynasty 1 tombs at Saqqara to the Djoser pyramid, the Giza Pyramids, and a selection of Dynasty 5 and 6 and Middle Kingdom pyramids. Samples were also taken from our excavations at Giza where two largely intact bakeries were discovered in 1991. The calibrated dates from the 1995 Old Kingdom pyramid samples tended to be 100 to 200 years older than the historical dates for the respective kings and about 200 years younger than our 1984 dates. The number of dates from both 1984 and 1995 was only large enough to allow for statistical comparisons for the pyramids of Djoser, Khufu, Khafre, and Menkaure. There are two striking results. First, there are significant discrepancies between 1984 and 1995 dates for Khufu and Khafre, but not for Djoser and Menkaure. Second, the 1995 dates are scattered, varying widely even for a single monument. For Khufu, they scatter over a range of about 400 years. By contrast, we have fair agreement between our historical dates, previous radiocarbon dates, and our radiocarbon dates on reed for the Dynasty 1 tombs at North Saqqara. We also have fair agreement between our radiocarbon dates and historical dates for the Middle Kingdom. Eight calibrated dates on straw from the pyramid of Senwosret II ranged from 103 years older to 78 years younger than the historical dates for his reign, with four dates off by only 30, 24, 14, and three years. Significantly, the older date was on charcoal.
Old Kingdom Problem. If the Middle Kingdom radiocarbon dates are okay, why are the Old Kingdom ones from pyramids so problematic? The pyramid builders used older cultural material, whether out of expedience or to make a conscious connection between their pharaoh and his predecessors. In galleries under the pyramid of the Dynasty 3 pharaoh Djoser more than 40,000 stone vessels were found. Inscriptions on them included most of the kings of Dynasty 1 and 2, but Djoser's name occurred only once. Perhaps Djoser gathered up the vases from the 200-year-old Archaic tombs at North Saqqara. In Dynasty 12, Amenemhet I actually took bits and pieces of Old Kingdom tomb chapels and pyramid temples (including those of the Giza Pyramids) and dumped them into the core of his pyramid at Lisht.
At Giza, south of the Sphinx, we are excavating remains of facilities for storage and production of fish, meat, bread, and copper that date to the middle and end of Dynasty 4, when the pyramids of Khafre and Menkaure were under construction. Three of the eight dates from samples taken here are almost direct hits on Menkaure's historical dates, 2532- 2504 B.C. The other five, however, range from 350 to 100 years older. Our radiocarbon dates from the site suggest that, like those from the pyramids, the dates on charcoal from the settlement scatter widely in time with many dates older than the historical estimate. The pyramid builders were likely recycling their own settlement debris.
It may have been premature to dismiss the old wood problem in our 1984 study. Do our radiocarbon dates reflect the Old Kingdom deforestation of Egypt? Did the pyramid builders devour whatever wood they could harvest or scavenge to roast tons of gypsum for mortar, to forge copper chisels, and to bake tens of thousands of loaves to feed the mass of assembled laborers. The giant stone pyramids in the early Old Kingdom may mark a major consumption of Egypt's wood cover, and therein lies the reason for the wide scatter, increased antiquity, and history-unfriendly radiocarbon dating results from the Old Kingdom, especially from the time of Djoser to Menkaure. In other words, it is the old-wood effect that haunts our dates and creates a kind of shadow chronology to the historical dating of the pyramids. It is the shadow cast by a thousand fires burning old wood.
While the multiple old wood effects make it difficult to obtain pinpoint age estimates of pyramids, the David H. Koch Pyramids Radiocarbon Project now has us thinking about forest ecologies, site formation processes, and ancient industry and its environmental impact--in sum, the society and economy that left the Egyptian pyramids as hallmarks for all later humanity.
The David H. Koch Pyramids Radiocarbon Project is a collaborative effort of Shawki Nakhla and Zahi Hawass, The Egyptian Supreme Council of Antiquities; Georges Bonani and Willy Wölfli, Institüt für Mittelenergiephysik, Eidgenossische Technische Hochschule; Herbert Haas, Desert Research Institute; Mark Lehner, The Oriental Institute and the Harvard Semitic Museum; Robert Wenke, University of Washington; John Nolan, University of Chicago; and Wilma Wetterstrom, Harvard Botanical Museum. The project is administered by Ancient Egypt Research Associates, Inc.