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.
As long as an organism lives it will take up new 14C, but from the moment it dies only decay takes place, i.e.
the radioactive isotope converts to stable, ordinary nitrogen atoms 14N.
At best, the method has an uncertainty of 25 years, and due to variations in intensity of cosmic rays there are periods in the Middle Ages and more recent times when the date obtained is very uncertain.
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. 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.
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. 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. and built the Giza Pyramids in a span of 85 years between 25 B. In spite of this discrepancy, the radiocarbon dates confirmed that the Great Pyramid belonged to the historical era studied by Egyptologists.
The most commonly used are radiocarbon and dendrochronological (tree-ring) dating.
Radiocarbon (14C) dating is based on the rate of decay of the unstable radioactive carbon isotope 14C present in all organic material.