Radiocarbon-Based Chronology for Dynastic Egypt

Abstract

The historical chronologies for dynastic Egypt are based on reign lengths inferred from written and archaeological evidence.
These floating chronologies are linked to the absolute calendar by a few ancient astronomical observations, which remain a
source of debate. We used 211 radiocarbon measurements made on samples from short-lived plants, together with a Bayesian model
incorporating historical information on reign lengths, to produce a chronology for dynastic Egypt. A small offset (19 radiocarbon
years older) in radiocarbon levels in the Nile Valley is probably a growing-season effect. Our radiocarbon data indicate that
the New Kingdom started between 1570 and 1544 B.C.E., and the reign of Djoser in the Old Kingdom started between 2691 and
2625 B.C.E.; both cases are earlier than some previous historical estimates.

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Radiocarbon-Based Chronology for Dynastic Egypt
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Radiocarbon-Based Chronology
for Dynastic Egypt
Christopher Bronk Ramsey,
1
*Michael W. Dee,
1
Joanne M. Rowland,
1
Thomas F. G. Higham,
1
Stephen A. Harris,
2
Fiona Brock,
1
Anita Quiles,
3
Eva M. Wild,
4
Ezra S. Marcus,
5
Andrew J. Shortland
6
The historical chronologies for dynastic Egypt are based on reign lengths inferred from
written and archaeological evidence. These floating chronologies are linked to the absolute
calendar by a few ancient astronomical observations, which remain a source of debate.
We used 211 radiocarbon measurements made on samples from short-lived plants, together
with a Bayesian model incorporating historical information on reign lengths, to produce a
chronology for dynastic Egypt. A small offset (19 radiocarbon years older) in radiocarbon levels
in the Nile Valley is probably a growing-season effect. Our radiocarbon data indicate that the
New Kingdom started between 1570 and 1544 B.C.E., and the reign of Djoser in the Old
Kingdom started between 2691 and 2625 B.C.E.; both cases are earlier than some previous
historical estimates.
Egyptian historical chronologies have been
underpinned by relative dating derived
from a variety of sources. Building on the
surviving evidence from Manetho’sAegyptiaca
(written in the third century B.C.E.) and the king
lists dating from the pharaonic era, generations
of scholars have used written and archaeological
information to check, and in some instances
revise, the sequence of kings and the lengths of
their reigns. Undocumented years at the ends of
some reigns and overlap between successive
monarchs create uncertainties of the order of a
few years (1).
The placement of this relative chronology
on the absolute-calendar time scale, however,
has been principally based on the interpreta-
tion of a small number of ancient astronomical
observations in the Middle and New King-
doms (MK and NK, respectively) and is there-
fore considerably less certain. Many of the
relevant celestial and lunar phenomena repeat
at regular intervals, giving different possible
chronologies, and their timing is dependent on
the location of the observer, which may also
add to the uncertainty (2). In addition, much
work has been done to synchronize the chro-
nology of Egypt to that of neighboring civ-
ilizations (3–5), particularly with Mesopotamia,
which also has a rich and detailed historical
record and astronomically based datums; how-
ever, precise absolute-age synchronisms be-
tween them are only possible in the late NK
(6). Radiocarbon dating, which is a two-stage
process involving isotope measurements and
then calibration against similar measurements
made on dendrochronologically dated wood,
usually gives age ranges of 100 to 200 years
for this period (95% probability range) and has
previously been too imprecise to resolve these
questions.
Here, we combine several classes of data to
overcome these limitations in precision: mea-
surements on archaeological samples that ac-
curately reflect past fluctuations in radiocarbon
activity, specific information on radiocarbon
activity in the region of the Nile Valley, direct
linkages between the dated samples and the
historical chronology, and relative dating in-
formation from the historical chronology. To-
gether, these enable us to match the patterns
present in the radiocarbon dates with the de-
tails of the radiocarbon calibration record and,
thus, to synchronize the scientific and histor-
ical dating methods. We obtained short-lived
plant remains from museum collections (e.g.,
seeds, basketry, plant-based textiles, plant stems,
fruits) that were directly associated with par-
ticular reigns or short sections of the historical
chronology. We avoided charcoal and wood
samples because of the possibility of inbuilt
1
Research Laboratory for Archaeology and the History of Art,
University of Oxford, Dyson Perrins Building, South Parks
Road, Oxford OX1 3QY, UK.
2
Department of Plant Sciences,
University of Oxford, South Parks Road, Oxford OX1 3RB, UK.
3
Laboratoire de Mesure du Carbone 14, bat 450 Porte 4E,
Commissariat à l’Energie Atomique (CEA)–Saclay, France-
Université Paris VII-Diderot, 91191 Gif-Sur-Yvette, France.
4
Vienna Environmental Research Accelerator Laboratory, Fakultät
für Physik, Isotopenforschung, Universität Wien, Währinger-
strasse 17, A-1090 Wien, Austria.
5
The Recanati Institute for
Maritime Studies, University of Haifa, Haifa 31905, Israel.
6
Centre for Archaeological and Forensic Analysis, Department of
Applied Science, Security and Resilience, Cranfield University,
Shrivenham, Swindon SN6 8LA, UK.
*To whom correspondence should be addressed. E-mail:
christopher.ramsey@rlaha.ox.ac.uk
Fig. 1. A selection of the
accession dates (first regnal
year) for the (A)OK,(B)MK,
and (C) NK derived from this
research. The marginal poste-
rior probability distributions
are shown in gray, with their
corresponding 95% probabil-
ity ranges indicated below.
Red, historical dates from Shaw
(18); blue, from Hornung et al.
(21); and green, from Spence
(24). The accession intervals
used for the model are from
Shaw (18), and corresponding
distributions using the inter-
vals from Hornung et al.(21)
are shown in fig. S4.
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age. We also avoided mummified material be-
cause of concerns about contamination from
bitumen or other substances used in the mum-
mification process and human material because
of the possibility of riverine or marine com-
ponents in the diet (which might contain older
carbon). We selected samples according to the
security of their archaeological context and
relation to a given king’s reign, but in making
the chronological associations, we were reliant
on the judgement of excavators and curators
and on the integrity of the collections them-
selves, because many of the excavations took
place in the 19th or early 20th century. Most of
the samples were taken from individual funerary
contexts. In a few cases, we sampled different
short-lived plant remains from a single context,
allowing us to check the internal consistency of
the measurements.
We prepared samples for radiocarbon anal-
ysis using standard acid-base-acid methods, in
some cases preceded by solvent extraction of
possible museum-based contaminants (7–10).
Next, we converted treated samples to graph-
ite (11) before radiocarbon measurement by ac-
celerator mass spectrometry (AMS) (12–14).
Calibration of the radiocarbon dates was against
the InCal04 calibration curve (15)usingOxCal
v4.1.3 (16,17). In all, we obtained 211 AMS
radiocarbon determinations (table S1). Where
there were indications of conservation work,
we attempted to avoid sampling the affected
areas and used solvent pretreatment methods
to remove potential contaminants, but the pos-
sibility remains that some cases of contamina-
tion may have escaped detection.
Fourteen of the ancient samples were actually
from the first or second millennium C.E. and
were thus clearly intrusive; we do not consider
these further. Another small set of radiocarbon
dates show offsets of a few hundred years
(typically younger than expected). This is not
surprising, as tomb contexts are often disturbed
after being sealed, and some intrusion of younger
material is always a possibility. Where we have
multiple samples from single contexts, the
internal agreement between the dates is usually
good, except for two measurements on the same
sample, where we suspect contamination, that are
not included in the analysis (see table S1 for
details).
In one case, although the internal con-
sistency is satisfactory, seven dates from one
single 19th Dynasty tomb are ~200 years older
than the historical age ascribed to them (see
dates ascribed to Ramses I/Seti I in table S1).
In this instance, we have concluded that there
must be an archaeological problem and have
excluded the dates from the model. We in-
cluded all other dates (188 in total), whether
or not they appear to be outliers in our anal-
ysis. We have 128 dates from the NK, 43 from
the MK, and 17 from the Old Kingdom (OK).
The majority (~75%) of the measurements
have calibrated age ranges that overlap with
the conventional historical chronology, within
the wide error limits that result from the cal-
ibration of individual dates.
To build a high-precision chronological se-
quence, we combined our radiocarbon measure-
ments with the historical information relating
to reign order and length. To do this, we adopted
a Bayesian modeling approach using the pro-
gram OxCal (16,17). For each major period
(OK, MK, and NK), we constructed a separate
multiphase model (16) with phase boundaries
set at the accession dates for the individual
rulers (or, in some cases, series of rulers). The
order of the reigns was defined but no prior
information was included on the absolute dat-
ing of the chronology. The dates for the samples
were constrained to lie in particular reigns (or,
in some instances, within several adjacent reigns),
and their associated calibrated radiocarbon mea-
surements were included as likelihoods in the
Bayesian model. The radiocarbon dates thus pro-
vide the only linkage in the model to the calendar
time scale.
We also included reign lengths as prior in-
formation relating to the intervals between the
successive accession dates, using the consensus
values from Shaw (18) as our estimates. Un-
certainties in reign lengths are small, especially
for the NK where they are typically 1 or 2 years,
though larger in a few specific cases such as for
Thutmose II and Horemheb. We quantify this
uncertainty in our model, but rather than using
the distribution N(0,1
2
), we use the Student’st
distribution (n= 5), which has longer tails to
provide a more robust result. For the MK, we
use an uncertainty that is three times that of the
NK [i.e., similar to a longer-tailed N(0,3
2
)]; for
the OK, the uncertainty is five times that of the
NK. These uncertainties are somewhat subjec-
tive, so we tested the models for robustness
under different choices of the scaling of these
uncertainties (fig. S2).
We also used environmental information
from a series of 66 AMS measurements on bo-
tanical specimens, with documented dates of
collection from Egypt in the period 1700 to
1900 C.E. These show a small but significant
depletion in radiocarbon levels relative to the
calibration curve (15), equivalent to a shift to
older radiocarbon dates of 19 T5 radiocarbon
years (
14
C yr) (19). This offset most likely re-
flects the unusual growing season in pre-
modern Egypt, which was concentrated during
the winter months after the annual inundation.
Plants in Egypt sampled the atmosphere at a
different time of the year than the trees mea-
sured for the calibration curve, and we might
expect a slight depletion because of the annual
fluctuation in the atmospheric radiocarbon
activity. The size of the effect agrees well with
the estimated peak-to-peak amplitude of the
seasonal fluctuations in radiocarbon activity in
the atmosphere of up to 4 per mil (<32
14
C yr)
for the pre-industrial era, produced by varia-
tions in the rate of transport of
14
C from the
stratosphere to the troposphere (20). We used
a single model parameter (DR) to model the
environmental offset, with a prior of N(19,5
2
).
Fig. 2. This figure shows the distribution of uncalibrated radiocarbon dates against the modeled
age. For each measurement, we show the mean and T1sof the radiocarbon and modeled calendar
dates: Points that have a low likelihood of being an outlier are shown with a gray point and black
error bars; those that are certain to be outliers are shown with gray error bars and white points
(see table S1 for outlier probabilities). The calibration curve is shown as two black lines (T1s). The
dates from the OK [(A) up to ~2300 B.C.E.] are concentrated in particular parts of the chronology;
most of the information comes from the start of the OK. For the MK [(A) from ~2100 B.C.E.], the
pattern of radiocarbon dates clearly reflects the distribution in the calibration curve, picking up
distinctive features present 1800 to 1900 B.C.E. and ~2000 B.C.E. (B) There are many more dates
shown in the NK, most of which are superimposed on each other and overlie the calibration curve,
picking up clear distinctive features of the curve, for example, around 1450 B.C.E. There is also a
scatter of outliers (shown in gray), but these show no systematic pattern and have no single
explanation.
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Because a proportion of the samples were ex-
pected to be out of context, we used t-type
outlier-modeling (17) with a prior outlier prob-
ability of 5%; we also tested the outcomes of
the model for robustness with a higher value of
this prior probability (see supporting online
material).
The modeling of the data provides a chronol-
ogy that extends from ~2650 to ~1100 B.C.E.
(Figs. 1 and 2 and Table 1). The benefits of using
the reign order and length information together
with the radiocarbon dates are greatest where
density of dates is highest. In the NK (128 dates),
the average calendrical precision is 24 years
[95% highest posterior density (hpd) range] for
accession dates (or 11 years for the 68% hpd
range). In the MK, where dates are sparser and
the uncertainty in the reign lengths is greater, the
average calendrical precision is 53 years (95%);
in the OK, where the number of dates is even
lower, the precision is 76 years (95%) but is still
markedly better than that possible with individual
measurements. Because reign length has been
included in our models, it is important to stress
that the outputs of the models cannot be used to
provide reign-length information.
The radiocarbon-based chronology for the
NK resolves different possible historical chro-
nologies (Fig. 1C). The radiocarbon dates chosen
for the NK are on samples from the 17th to the
21st Dynasties, which provide brackets beyond
the beginning and end of the NK. However,
there are no dates for specific reigns before that
of Thutmose III, and so dates earlier than this
are based primarily on the reign-length infor-
mation included in the model. The agreement is
closest to the consensus chronology compiled
by Shaw (18), in which the NK starts in 1550
B.C.E. and from which we take our reign lengths.
It rules out some of the other interpretations
proposed (21–23) that are somewhat later,
even if different reign lengths and overlaps are
considered (fig. S3A). The radiocarbon dates
imply that the NK might have begun earlier
by about a decade than the consensus date of
Shaw, which would imply either shorter over-
laps or a slight extension to some reigns in the
sequence.
In the MK, the conventional (and earlier)
historical chronology (1) is largely based on a
single observation of the heliacal rising of the
star Sothis (Sirius). Different interpretations
of this and other astronomical observations
are possible, depending on the supposed point
of observation, and a chronology that is about
40 years younger has also been put forward,
based more on lunar observations (21–23).
The radiocarbon chronology favors the earlier
interpretation, but it cannot be used to decide
conclusively between these interpretations
(Fig. 1B).
The results for the OK, although lower in
resolution, also agree with the consensus chronol-
ogy of Shaw (18) but have the resolution to con-
tradict some suggested interpretations of the
evidence, such as the astronomical hypothesis
of Spence (24), which is substantially later, or
the reevaluation of this hypothesis (25), which
leads to a date that is earlier. The absence of
astronomical observations in the papyrological
record for the OK means that this data set
provides one of the few absolute references for
the positioning of this important period of
Egyptian history (Fig. 1A).
Thus, the radiocarbon measurements provide
a coherent chronology for ancient Egypt, which
is in good agreement with some earlier attempts
to tie down the floating chronology. In contrast,
a previous large-scale radiocarbon study gave
dates that were substantially earlier than the ex-
pected ages for the OK (26) and dates that are
earlier than expected at Tell el-Dab
c
a(27).
These discrepancies probably reflect the choice
Table 1. Modeled accession dates (first regnal year) for selected kings and queens in the Egyptian
historical chronology based on the new radiocarbon data (this paper) and reign accession intervals
from Shaw (18) (see tables S7 and S8 for full lists) compared with other estimates (18,21). The
number of radiocarbon dates for individual reigns included in the models is shown (full details are
in table S1). 0, reigns for which we have no dates; ND, not determined.
King/queen
No.
14
C
dates
in
models
Accession dates (B.C.E.)
Shaw
(18)
Hornung
et al.
(21)
Modeled hpd ranges
68% 95%
from to from to
Old Kingdom
Djoser 7 2667 2592 2676 2643 2691 2625
Sneferu 2 2613 2543 2634 2599 2649 2582
Khufu 0 2589 2509 2613 2577 2629 2558
Djedefra 0 2566 2482 2593 2556 2610 2536
Khafra 0 2558 2472 2586 2548 2604 2528
Menkaura 0 2532 2447 2564 2524 2581 2504
Shepseskaf 0 2503 2441 2538 2498 2556 2476
Userkaf 0 2494 2435 2530 2489 2548 2468
Sahura 0 2487 2428 2524 2482 2542 2460
Djedkara 1 2414 2365 2473 2432 2486 2400
Unas 0 2375 2321 2438 2397 2450 2363
Teti 0 2345 2305 2412 2370 2423 2335
7 Further dates from the Second to Eighth Dynasties
Middle Kingdom
Mentuhotep II 9 2055 2009 2057 2040 2064 2019
Amenemhat I 4 1985 1939 1991 1973 1998 1952
Senusret I 1 1956 1920 1965 1945 1971 1924
Amenemhat II 0 1911 1878 1922 1901 1928 1878
Senusret II 2 1877 1845 1890 1868 1895 1844
Senusret III 10 1870 1837 1884 1860 1889 1836
Amenemhat III 10 1831 1818 1844 1820 1851 1798
Amenemhat IV 0 1786 1772 1799 1773 1809 1753
Sobekneferu 0 1777 1763 1790 1764 1801 1744
Wegaf 0 1773 1759 1785 1758 1797 1739
7 Further dates from the 11th to 13th Dynasties
New Kingdom
Ahmose 0 1550 1539 1566 1552 1570 1544
Amenhotep I 0 1525 1514 1541 1527 1545 1519
Thutmose III 24 1479 1479 1494 1483 1498 1474
Hatshepsut 25 1473 1479 1488 1477 1492 1468
Amenhotep II 1 1427 1425 1441 1431 1445 1423
Amenhotep III 2 1390 1390 1404 1393 1408 1386
Amenhotep IV 17 1352 1353 1365 1355 1370 1348
Tutankhamun 7 1336 ND 1349 1338 1353 1331
Horemheb 0 1323 1319 1336 1325 1341 1318
Rameses I 0 1295 1292 1308 1297 1313 1290
Rameses II 2 1279 1279 1292 1281 1297 1273
Sethnakht 0 1186 1190 1198 1187 1204 1179
Rameses III 0 1184 1187 1196 1185 1202 1176
Rameses IX 2 1126 1129 1137 1127 1143 1117
Rameses XI 0 1099 1106 1110 1100 1116 1090
48 Further dates from the 17th to 21st Dynasties
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of samples for dating. Many of the sites in an-
cient Egypt were densely populated over long
periods (a notable exception being Amarna). In
addition, some resources, such as wood, were in
short supply. Reuse of scarce resources can result
in the incorporation of older organic material,
particularly wood and charcoal, into younger
deposits. The long use, revisiting, and robbing of
some monuments also provide opportunities
for later organic material to be discovered in
earlier contexts. We were able to reduce, but not
eliminate, such outliers by selecting only short-
lived plants from secure contexts. Despite these
precautions, we still found a significant number
of young outliers among the dates measured,
which we accounted for by using Bayesian
outlier analysis.
To test the sensitivity of our analysis to the
parameters of the model, we looked at the effect
of altering the uncertainty in the reign lengths,
alternative reign-length estimates (21), and the
prior outlier probability (figs. S2 to S4). We also
evaluated the effect of applying a different prior
for DR. The main model uses a prior of N(19,5
2
),
based on the environmental information (19). If
we use a more neutral prior of N(0,10
2
)forthe
NK where we have most dates, the chronology is
virtually unaltered (fig. S5), and the posterior for
DRis also similar (Fig. 3). This shows that the
ancient samples independently confirm a local
offset in radiocarbon of 20 T5 years, because the
pattern of radiocarbon dates found through the
NK fits better with the calibration curve when
such an offset is applied.
The confirmation of a small regional offset
will need to be considered in the calibration of
all radiocarbon dates from the Nile region.
The small size of this offset implies that pre-
vious studies that have seen much larger offsets
(26,27) are probably due to sample selection or
context.
This radiocarbon-based chronology for the
dynastic period allows direct comparison to the
radiocarbon records of predynastic sites in Egypt,
and those from the neighboring regions of Libya
and Sudan, which is a prerequisite for understand-
ing the speed and mechanisms of Egyptian state
formation. This chronology also has implications
for the wider Mediterranean and surrounding
regions that rely on linkages to Egypt to anchor
their own chronologies (3–5). For the second
millennium B.C., for example, it will contribute
to our understanding of the differences between
the historical Aegean chronology, derived from
linkages with Egypt (27), and the radiocarbon
record for that region, and specifically, for the
Minoan eruption of Santorini (28,29). More
widely, Egypt and Mesopotamia are the only parts
of the western Old World that have written records
spanning the Bronze and Iron ages, and they are
linked by trade with regions that stretch from
Central Asia to the western Mediterranean and
down into Nubia. Chronology is key to under-
standing the nature of these linkages, and the
harmonization of the historical chronologies of
Egypt with the calibrated radiocarbon time scale
removes a fault line between regions dated scien-
tifically and those tied into historical sequences.
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30. This project was funded by the Leverhulme Trust
(grant no. F/08 622/A). The botanical specimens were
from the Oxford University Herbaria and the Natural
History Museum, London. Archaeological samples were
from Ägyptisches Museum und Papyrussammlung,
Berlin; Ashmolean Museum, Oxford; Bolton Museum
and Art Gallery; British Museum, London; City Museum
and Art Gallery, Bristol, UK; Cornell University, New
York; Desert Research Institute, Las Vegas, Nevada;
Kunsthistorisches Museum, Vienna; The Manchester
Museum; Medelhavsmuseet, Stockholm; Metropolitan
Museum of Art, New York; Musée du Louvre, Paris;
Musées royaux d’art et d’histoire, Brussels; National
Museums, Liverpool, UK; The Petrie Museum of Egyptian
Archeology, London; The Pitt Rivers Museum, Oxford;
Royal Botanic Gardens, Kew, UK; Staatliches Museum
Ägyptischer Kunst, Munich; and the Victoria Museum of
Egyptian Antiquities, Uppsala University, Sweden. The
Oxford laboratory infrastructure was funded by the
Natural Environment Research Council and software
development by English Heritage. The Illahun,
Heqanakht, and Hatshepsut measurements and research
were funded by the German-Israeli Foundation for
Scientific Research and Development (grant no. I-2069-
1230.4/2004); preliminary background research was
aided by the SCIEM2000 project. The dating at Saclay
was performed at the LMC14 (funded by CNRS, CEA,
Institut de Radioprotection et de Sûreté Nucléaire,
Institut de Recherche pour le Développement, and
MinistèredeLaCulture).
Supporting Online Material
www.sciencemag.org/cgi/content/full/328/5985/1554/DC1
Materials and Methods
SOM Text
Figs. S1 to S5
Tables S1 to S7
References
10 March 2010; accepted 3 May 2010
10.1126/science.1189395
Fig. 3. Systematic re-
gional offset in radio-
carbon dates from the
calibration curve. (A)In
our model, we have used
a prior for the regional
offset of 19 T5
14
Cyr,as
shown by the light gray
region; the posterior den-
sity for the NK (dark gray
region) confirms the as-
sumed value for this peri-
od. (B)If weuseamuch
more neutral prior for
this offset of 0 T10, the
posterior for this param-
eter is almost unchanged,
showing that the ancient
data support such an
offset independently.
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