The number of dates from the two projects was only large enough to allow for statistical comparisons for the pyramids of Djoser, Khufu, Khafre, and Menkaure. First, there are significant discrepancies between the 19 dates for Khufu and Khafre, but not for Djoser and Menkaure.
Second, the 1995 dates vary widely even for a single monument.
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 (1897-1878 BC) ranged from 103 years older to 78 years younger than the historical dates for his reign.
Ancient Egypt’s population was restricted to the narrow confines of the Nile Valley with, we assume, a sparse cover of trees.But material from the time of the pyramids lends itself well to radiocarbon dating because they fall into the 2575-1640 date range.Radiocarbon technicians prefer to test wood and wood charcoal because their high molecular weight mitigates material loss during the rigorous pretreatments required for radiocarbon testing.The earliest experiments in radiocarbon dating were done on ancient material from Egypt. Libby’s team obtained acacia wood from the 3rd Dynasty Step Pyramid of Djoser to test a hypothesis they had developed.Libby reasoned that since the half-life of C years, the Djoser sample’s C14 concentration should be about 50% of the concentration found in living wood (for further details, see Arnold and Libby, 1949). Subsequent work with radiocarbon testing raised questions about the fluctuation of atmospheric C14 over time.