Claims › Egypt: Sphinx & Giza dating › Radiocarbon dates from Giza mortar fall in the Old Kingdom era, with an unresolved offset

Radiocarbon dates from Giza mortar fall in the Old Kingdom era, with an unresolved offset

Status: Mainstream Verdict: Measured: mortar charcoal dates to c. 2900–2600 BCE; the cause of a 100–400-year offset is still debated

The claim: Radiocarbon dates on charcoal and plant fragments in the Giza pyramids' mortar place the dated construction in the Old Kingdom era, not thousands of years earlier, though the dates run older than Khufu's reign.

Why this label: Two sampling campaigns (1984 and 1994–95) produced 269 radiocarbon measurements on Old and Middle Kingdom monuments, 46 of them from the Great Pyramid. The results consistently fall around 2900–2600 BCE: centuries, not millennia, older than the historical dates. Why they run old (old wood, recycled fuel, or something else) is an inference that has not been directly tested at Giza, and no short-lived plant material from the Great Pyramid itself has been dated.

Background

The pyramids' mortar is mainly gypsum, which contains no carbon of its own. What can be dated are the tiny flecks of charcoal, ash and plant matter mixed in from the fires used to make it. The 1984 campaign, funded by supporters of Edgar Cayce (who had claimed a date of 10,500 BCE), found that dates from Dynasty 3–5 monuments averaged 374 years older than the historical chronology; that figure covers the whole Old Kingdom set, not the Great Pyramid alone. The larger 1994–95 campaign came out 100–200 years older, with wide scatter. The project team first judged an 'old wood' explanation unlikely, then concluded it had been premature to dismiss it: long-lived trees, stored timber and recycled fuel all make charcoal look older than the fire. A 2009 Bayesian reanalysis that models completion dates instead of averages, and uses the order of the kings as a prior assumption, brings the dates into close agreement with the historical record; its authors note that their calibrations do not depend on the old-wood interpretation being right. Separate chronologies built only from short-lived plants agree with the historical Old Kingdom. The dates say nothing about parts of the site that contain no sampled mortar, which is the point raised by the legacy hypothesis. See also the Sphinx water-erosion claim.

What has been measured

Dates, measurements and documented findings, kept separate from interpretation.

1984 campaign: dates from Dynasty 3–5 monuments averaged 374 years older than the historical chronology. [2][3]
1994–95 campaign: Old Kingdom pyramid dates ran about 100–200 years older than the historical dates. For Khufu they scatter over about 400 years, and the two campaigns disagree significantly for Khufu and Khafre. [1][3]
Great Pyramid: 46 measurements, almost all on charcoal from mortar in exposed outer courses and the summit, with a weighted mean of 4147 ± 10 radiocarbon years BP. The authors' calibration gives about 2870–2600 BCE (two-sigma), against a historical reign of 2589–2566 BCE. [1]
The cedar fragment found in the Queen's Chamber in 1872 (the Dixon relic) dated to 3341–3094 cal BCE. [7][8]
Chronologies built only from short-lived plants (not pyramid mortar) support the historical Old Kingdom: 211 measurements in 2010, only 17 of them from the Old Kingdom, placed Khufu's accession at about 2629–2558 BCE (95%); a 2025 study with 33 Old Kingdom dates supports the 'High' chronology. [5][6]

Evidence and arguments for

Old wood, inner tree rings and recycled fuel can only make charcoal dates too old. Straw and reed from other monuments give much smaller offsets. [2][4]
A Bayesian reanalysis that models completion dates rather than averages puts the Great Pyramid's completion at 2620–2484 cal BCE (95%). It uses the order of the kings as a prior assumption. [4]
Papyri from Khufu's Red Sea harbour record crews shipping Tura limestone to 'Akhet-Khufu' in about Year 26 of his reign, under his vizier Ankhhaf. This evidence is independent of radiocarbon. [9]

Evidence and arguments against, or limits

The old-wood effect was first judged unlikely by the project team and has never been measured directly at Giza; the 2009 reanalysis states that its size remains unknown. [2][4]
All Great Pyramid samples came from the exterior. The dates cannot test whether the inner core, the bedrock mound or the subterranean chamber is older, as Robert Schoch proposes. [1][12]
The only dated object from the interior (the Dixon cedar) is about 500 years older than Khufu. Old wood is one explanation, but it is not proven. [7]
Gypsum mortar has no datable carbon of its own, so the dates rest entirely on charcoal and ash mixed in from fires. [10][11][1]

Open questions & what would change the label

AMS dates on reed, straw or seeds from secure inner joints of the Great Pyramid, species and ring-count analysis of the mortar charcoal, and a re-run of the 1984 samples with modern pretreatment would test the offset directly. Dating the bedrock-cut and subterranean parts would need a different method, such as surface exposure dating.

Sites

Giza pyramids · Great Sphinx of Giza

Related claims

Sources

Bonani, G. et al. (2001). Radiocarbon dates of Old and Middle Kingdom monuments in Egypt. Radiocarbon 43(3). doi:10.1017/s0033822200038558 data
Members of the David H. Koch Pyramids Radiocarbon Project (1999). Dating the Pyramids. Archaeology 52(5). https://archive.archaeology.org/9909/abstracts/pyramids.html data
AERA (Ancient Egypt Research Associates). How old are the pyramids? Project summary of the 1984 and 1995 radiocarbon programmes. https://aeraweb.org/projects/how-old-are-the-pyramids/ background
Dee, M. W. et al. (2009). Reanalysis of the chronological discrepancies obtained by the Old and Middle Kingdom Monuments Project. Radiocarbon 51(3). doi:10.1017/s0033822200034111 data
Bronk Ramsey, C. et al. (2010). Radiocarbon-based chronology for dynastic Egypt. Science 328. doi:10.1126/science.1189395 data
Erdil, P. et al. (2025). Resolution of the High versus Low debate for Old and Middle Kingdom Egypt. PLOS One 20(5): e0314612. doi:10.1371/journal.pone.0314612 data
Curtis, N. G. W. & Eladany, A. (2020). Pyramidology and radiocarbon: the dating and interpretation of a fragment of wood from the Great Pyramid. CIPEG Journal 4. doi:10.11588/cipeg.2020.4.86467 data
University of Aberdeen (16 December 2020). Missing 5,000-year-old piece of Great Pyramid puzzle discovered in cigar box in Aberdeen (news release). https://www.abdn.ac.uk/news/14573/ background
Tallet, P. (2017). Les papyrus de la mer Rouge I: le 'journal de Merer' (MIFAO 136). IFAO, Cairo (publisher's summary). https://www.ifao.egnet.net/uploads/publications/divers/MIFAO136_ann_01.pdf data
Regourd, M., Kerisel, J., Deletie, P. & Haguenauer, B. (1988). Microstructure of mortars from three Egyptian pyramids. Cement and Concrete Research 18(1). doi:10.1016/0008-8846(88)90124-x data
Hemeda, S. & Sonbol, A. (2020). Sustainability problems of the Giza pyramids. Heritage Science 8: 8. doi:10.1186/s40494-020-0356-9 data
Robert Schoch on The Joe Rogan Experience #1124 (2018), transcript. https://jre.ai/episodes/1124-robert-schoch/transcript proponent
Ghoneim, E. et al. (2024). The Egyptian pyramid chain was built along the now abandoned Ahramat Nile Branch. Communications Earth & Environment 5. doi:10.1038/s43247-024-01379-7 data
Sheisha, H. et al. (2022). Nile waterscapes facilitated the construction of the Giza pyramids during the 3rd millennium BCE. PNAS 119. doi:10.1073/pnas.2202530119 data

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Sources checked against Crossref and publisher pages on 2026-10-22. Labels describe the claim, not the people who hold it. Methodology.