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Radiocarbon dates and Bayesian modeling support
maritime diffusion model for megaliths in Europe
B. Schulz Paulsson
a,1
a
Department of Historical Studies, University of Gothenburg, SE-405 30 Gothenburg, Sweden
Edited by James F. O’Connell, University of Utah, Salt Lake City, UT, and approved January 3, 2019 (received for review August 1, 2018)
There are two competing hypotheses for the origin of megaliths in
Europe. The conventional view from the late 19th and early 20th
centuries was of a single-source diffusion of megaliths in Europe
from the Near East through the Mediterranean and along the
Atlantic coast. Following early radiocarbon dating in the 1970s, an
alternative hypothesis arose of regional independent develop-
ments in Europe. This model has dominated megalith research
until today. We applied a Bayesian statistical approach to 2,410
currently available radiocarbon results from megalithic, partly
premegalithic, and contemporaneous nonmegalithic contexts
in Europe to resolve this long-standing debate. The radiocarbon
results suggest that megalithic graves emerged within a brief time
interval of 200 y to 300 y in the second half of the fifth millennium
calibrated years BC in northwest France, the Mediterranean, and
the Atlantic coast of Iberia. We found decisive support for the
spread of megaliths along the sea route in three main phases.
Thus, a maritime diffusion model is the most likely explanation of
their expansion.
megaliths
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mobility
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radiocarbon dates
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Bayesian analysis
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megalithic seafaring
There are ∼35,000 presently extant European megaliths, a
term which is derived from Greek μέγας (mégas), “big,”and
λίϑoς(líthos), “stone.”These include megalithic tombs, standing
stones, stone circles, alignments, and megalithic buildings or
temples. Most of these were constructed during the Neolithic
and the Copper Ages and are located in coastal areas. Their
distribution is along the so-called Atlantic façade, including
Sweden, Denmark, North Germany, The Netherlands, Belgium,
Scotland, England, Wales, Ireland, northwest France, northern
Spain, and Portugal, and in the Mediterranean region, including
southern and southeastern Spain, southern France, the Islands
of Corsica, Sardinia, Sicily, Malta and the Balearics, Apulia,
northern Italy, and Switzerland. Interestingly, they share similar
or even identical architectonic features throughout their distri-
bution. Megalithic graves were built as dolmens and as passage
or gallery graves (Figs. 1 and 2). Thousands of anthropogenic
erected stones either stand isolated in the landscapes or were
arranged as circles or in rows. There is evidence all across
Europe for an orientation of the graves toward the east or
southeast in the direction of the rising Sun. The question
therefore arises whether there was a single, original source from
which a megalithic movement spread over Europe or regional
phenomena developed independently due to a similar set of
conditions. Earlier research provided two very different answers
to the question of origins. During the later 19th and the first two-
thirds of the 20th centuries, archaeologists such as Montelius (1),
Childe (2, 3), and Daniel (4) proposed models of a single origin
of megaliths from which they then expanded by a process of
diffusion. Thus, Montelius (1), in the Ex Oriente Lux Zeitgeist of
the late 19th century, advocated for the Near East as a potential
region of origin. Childe (5), building on Montelius, supported
theideaofadiffusionof“oriental culture”by maritime ex-
change. According to Childe (6), the expansion was supported by
a megalithic religion of migrant priestly elites who settled down
long enough among local societies for the new ideas to take root.
He proposed a route from the Mediterranean to the Atlantic
northwest across the Pyrenean isthmus and an onward dissemi-
nation of the megalithic tradition from there to Britain and then
later over the sea route around Spain and Portugal. Later, Childe
(2, 3) expanded his theory about the spreading of a megalithic
religion along the coastlines of western Europe by way of mis-
sionaries or prospectors. With the introduction of radiocarbon
dates and processual approaches, the idea of an independent
emergence of the same kind of stone architecture in several re-
gions arose, because early C14 results did not support the dif-
fusion model. Renfrew (7) was the first to exploit the new
chronological results and proposed five independent nucleus
centers, including Portugal, Andalusia, Brittany, southwest
England, Denmark, and possibly Ireland for the emergence of
megaliths in Europe. The model of an independent emergence
of megaliths in several regions and sedentary, immobile farming
communities has remained dominant in the research literature
since then (8–10). However, since the 1970s, the number of C14
dates of megaliths has expanded enormously. It is therefore
timely to test the two prevailing interpretative models in the light
of this new evidence.
For this end, we investigated the fine-grain temporal pattern
for the emergence of megaliths in Europe with the analysis of
2,410 available radiocarbon dates taken from premegalithic,
megalithic, and nonmegalithic but contemporaneous contexts
(Dataset S1). Radiocarbon dating is a two-stage process in-
volving isotope measurements and the calibration against similar
measurements made on dendrochronologically dated wood.
For our time horizon, it normally provides precision ranges of
100 y to 300 y with 95% probability. To build a chronological
Significance
For thousands of years, prehistoric societies built monumental
grave architecture and erected standing stones in the coastal
regions of Europe (4500–2500 calibrated years BC). Our un-
derstanding of the rise of these megalithic societies is con-
tentious and patchy; the origin for the emergence of megalithic
architecture in various regions has been controversial and de-
bated for over 100 y. The result presented here, based on
analyses of 2,410 radiocarbon dates and highly precise chro-
nologies for megalithic sites and related contexts, suggests
maritime mobility and intercultural exchange. We argue for the
transfer of the megalithic concept over sea routes emanating
from northwest France, and for advanced maritime technology
and seafaring in the megalithic Age.
Author contributions: B.S.P. designed research, performed research, analyzed data, and
wrote the paper.
The author declares no conflict of interest.
This article is a PNAS Direct Submission.
This open access article is distributed under Creative Commons Attribution-NonCommercial-
NoDeriv atives License 4.0 (CC BY-NC-ND).
1
Email: bettina.schulz.paulsson@gu.se.
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megalithic sequence as precisely as possible, we adopted a
Bayesian modeling approach, which is applied here to a wide
region, using the program OxCal 4.1 (11, 12). We combined
measurements with archaeological information relating to
stratigraphical contexts, associated cultural material, and in-
formation on the burial rites, to narrow the time intervals for the
calibrated ranges. In a first important step, we reviewed critically
the 2,410 samples, including measurements from the 1960s up to
the present, to determine the quality and reliability of the sample
contexts. For each site with available radiocarbon results and a
suitable sequence, we constructed one-phased or multiphased
models with phase boundaries (Datasets S2 and S3) taking into
consideration the detailed stratigraphic information (13). The
posterior density estimates expressed as probability distribu-
tions in the text and in the figures are given by convention
in italics to distinguish them clearly from simple calibrated
radiocarbon dates.
Results
The radiocarbon dates suggest that the first megalithic graves in
Europe were closed small structures or dolmens built above-
ground with stone slabs and covered by a round or long mound
of earth or stone. These graves emerge in the second half of the
fifth millennium calibrated years (cal) BC within a time interval
of 4794 cal BC to 3986 cal BC (95.4%;4770 cal BC to 4005 cal
BC,68.2%)(Dataset S3,M7-2 to M29-4), which can be reduced
most probably to 200 y to 300 y, in northwest France, the
Channel Islands, Catalonia, southwestern France, Corsica, and
Sardinia. Taking the associated cultural material into consider-
ation, megalithic graves from Andalusia, Galicia, and northern
Italy presumably belong to this first stage (Fig. 3). There are no
radiocarbon dates available from the early megalithic graves in
these regions, or their calibrated ranges show an onset extending
into the fourth millennium cal BC, as is the case for Galicia. Of
these regions, northwest France is the only one which exhibits
monumental earthen constructions before the megaliths (SI
Appendix, Fig. S2). The Passy graves in the Paris Basin have no
megalithic chamber yet, but are impressive labor-intensive
structures with a length of up to 280 m. These graves seem to
be the earliest monumental graves in Europe; the first individual
buried in the Passy necropolis died in 5061 cal BC to 4858 cal BC
(95.4%;5029 cal BC to 4946 cal BC,68.2%)(Dataset S3,M1-4).
Somewhat later, the first monumental graves emerge in Brittany,
and especially in the region of Carnac, in the form of round
tumuli covering pit burials, stone cists, and dry-wall chambers.
The first building phase of the tumulus St. Michel in Carnac is
dated to the time interval 4782 cal BC to 4594 cal BC (95.4;4724
cal BC to 4618 cal BC,68.2%)(Dataset S3,M4-2 to M4-4).
The earliest megalithic grave chambers in Brittany, such as
Tumiac, Kervinio, Castellic, St. Germain, Manio 5, Mané
Hui, and Kerlescan (14–16), emerge within this horizon as an
architectonic feature of monumental long and round mounds.
For these early megaliths, no radiocarbon determinations are
available. It is only possible to limit the time interval of con-
struction to the Ancient Castellic horizon based on the typo-
chronological considerations of the grave goods and according to
Ancient Castellic contexts with associated radiocarbon results
ranging from 4794 cal BC to 3999 cal BC (95.4%;4770 cal BC
to 4034 cal BC,68.2%)(Dataset S3,M7-2 to M7-7).
In Catalonia, in the Tavertet region, early megalithic graves
emerged during the same time interval, even contemporaneous
with the graves in Brittany. A reevaluation of the available ra-
diocarbon results yielded a dating of the construction of these
graves not before 4722 cal BC to 4068 cal BC (95.4%;4581 cal
BC to 4267 cal BC,68.2%)(Dataset S3,M24-33). A part of these
data exhibit an inbuilt age (Dataset S3,M24-28 to M24-32) (ref.
13, p. 128). On the northeastern side of the Pyrenees in southern
France, early megaliths are either isolated in the landscape or
arranged in necropolises as at Najac and Camp del Ginèbre. The
unmodeled ranges of three radiocarbon results for human bones
from the necropolis of Najac 4328 cal BC to 3979 cal BC (95.4%;
4318 cal BC to 3995 cal BC) (Dataset S1,830 to 832) suggest
burials within this time horizon. Along the central Mediterra-
nean coasts and north Mediterranean islands of Sardinia and
Corsica, small necropolises are found with early megalithic
graves. The grave goods from the Li Muri necropolis on Sardinia
are attributed to the Late Neolithic San Ciriaco horizon, and,
according to the radiocarbon results from the San Ciriaco layers
in the settlement of Contraguda, it is possible to limit the
emergence of these graves to a time interval from 4733 cal BC to
3986 cal BC (95.4%;4471 cal BC to 4005 cal BC,68.2%)
(Dataset S3,M29-1 to M29-4). There are further clusters with
potential early megalithic graves documented in the central
Mediterranean in northern Italy, for example, in La Vela-
Trento, or Maddalena di Chiomonte-Torino and possibly Apu-
lia (6). However, for these, there are no radiocarbon dates
available yet. Based on the archaeological material, they are
likely dated to the second half of the fifth millennium cal BC.
From the southwest Iberian Peninsula in Andalusia, the Algarve,
and the Alentejo, we find more of these possible early megaliths
(17–19).
In the northern half of the western Iberian Peninsula, there
are early megaliths, concentrated mainly in Galicia. So far, these
Fig. 1. Dolmen de las Ruines, Catalonia. Photo courtesy of B.S.P.
Fig. 2. Haväng dolmen, Scania. Strikingly, the architectonic concepts of megaliths
are similar or even identical all over Europe. Photo courtesy of B.S.P.
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have been dated to the very end of the fifth millennium cal BC, if
not later. Most of these dates are from charcoal, and many
represent termini post quos values due to the inbuilt age of the
wood or unsure contexts. From Chan de Cruz 1, a possible
construction or usage date from ∼4080 cal BC (CSIC-642,
5210 ±50 BP, 4144 cal BC to 3961 cal BC, 68.2%; 4230 cal
BC to 3947 cal BC, 95.4%) (Dataset S1,2014) is available.
Small stone chambers with no access and single or double
inhumations are diagnostic for the early megalithic stage in the
fifth millennium cal BC. In the last third of the fifth millennium,
the earliest chambers with access are attested as dolmens and
passage graves (Fig. 4). These graves could be reopened for re-
peated burials, and this marks the beginning of a new practice for
the whole of Europe: the construction of graves for successive
depositions of human remains over centuries. The earliest known
accessible megalithic grave with reliable radiocarbon dates is
located in central western France in the necropolis of Prissé-la-
Charrière, Deux-Sèvres. The beginning of burial activities at this
dolmen is calculated at 4371 cal BC to 4263 cal BC (95.4%;4358
cal BC to 4275 cal BC,68.2%)(Dataset S3,M20-2). Structures
transitional to passage graves are documented for Brittany and
for the long tumulus or tertre of Lannec er Gadouer with a ra-
diocarbon sequence which pinpoint this transition to 4503 cal BC
to 4103 cal BC (95.4%;4432 cal BC to 4233 cal BC,68.2%)
(Dataset S3,M5-8). Contemporaneous accessible megalithic
graves are known from northern Corsica on the Monte Revincu
dated at 4327 cal BC to 4266 cal BC (95.4%;4302 cal BC to 4273
cal BC,68.2%)(Dataset S3,M27-5).
On the western Iberian Peninsula, date ranges for the onset
of accessible structures are calculated for the Estremadura at
3844 cal BC to 3383 cal BC (95.4%;3658 cal BC to 3432 cal
BC,68.2%)(Dataset S3,M33-1), for the Alentejo at 3743 cal
BC to 3521 cal BC (95.4%;3673 cal BC to 3567 cal BC,68.2%)
(Dataset S3,M34-5), and for Beira at 3883 cal BC to 3782 cal
BC (95.4%;3837 cal BC to 3796 cal BC,68.2%)(Dataset S3,
M35-19). Similarly, the earliest megaliths with entrance in
BritainandIrelandarealsocalculatedtothefirsthalfofthe
fourth millennium cal BC. The earliest known megalithic
grave in southeast England, Coldrum, is calculated at 3971 cal
BC to 3805 cal BC (95.4%;3960 cal BC to 3880 cal BC,68.2%)
(20), and Parknabinnia on the Burren in Ireland at 3885 cal
BC to 3440 cal BC (95%;3715 cal BC to 3530 cal BC,
68%) (21).
The subsequent centuries are a time of megalithic stasis and
reuse of ancient megalithic graves. With the exception of the
gallery graves in Belgium, there is no evidence for movements or
new megalithic regions added at this time.
Finally, an even later megalithic expansion occurred in the
second half of the fourth millennium in northern Germany and
southern Scandinavia (22–24). In the Mediterranean, there is
a megalithic revival in the second millennium cal BC in the
Fig. 3. Map showing dates estimated for the start of megaliths in the different European regions, with 95% probability (68% probability in brackets). Italic
bold type is used for date ranges of the posterior density estimates based on samples from megalithic contexts, regular bold type is used for simple calibrated
radiocarbon dates from megalithic contexts, and regular italic type is used for the probabilities of the posterior density estimates associated with the earliest
cultural material in the megaliths.
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ANTHROPOLOGYSTATISTICS
Balearic Islands, Apulia, and Sicily. These are associated with
the Bronze Age and/or with the Bell Beaker phenomena (25).
Discussion
The radiocarbon results suggest that megalithic graves emerged
within a time interval of 200 y to 300 y in the second half of the
fifth millennium cal BC in northwest France, the Mediterranean,
and the Atlantic coast of the Iberian Peninsula. Northwest
France is, so far, the only megalithic region in Europe which
exhibits a premegalithic monumental sequence and transitional
structures to the megaliths, suggesting northern France as
the region of origin for the megalithic phenomenon. For the
remaining regions with an early megalithic proliferation in
the fifth millennium cal BC (such as Catalonia, southern France,
Corsica, Sardinia, and probably the western Iberian Peninsula
and Italian mainland), megaliths are found occurring in small
clusters. These are exceptional grave forms for this period in
their respective regions, at a time when subterranean cists, pit
burials and hypogea (dug-out subterranean burial chambers)
were still the most common burial rites. A fresh expansion oc-
curred during the first half of the fourth millennium cal BC when
thousands of passage graves were built along the Atlantic coast
of the Iberian Peninsula, Ireland, England, Scotland, and France.
Their distribution emphasizes the maritime linkage of these so-
cieties and a diffusion of the passage grave tradition along the
seaway. The passage graves mark a radical change of burial rites,
along with other economic and social changes in Europe. In the
second half of the fourth millennium cal BC, the passage grave
tradition finally reaches Scandinavia and the Funnel Beaker
areas. Again, there is evidence for the spread of megalithic
architecture along the seaway. The first known passage graves
in Scandinavia were built on the western coasts of the Swedish
Islands Oland and Gotland, which are both situated in the
Baltic (23).
We have thus been able to demonstrate that the earliest
megaliths originated in northwest France and spread along the
sea routes of the Mediterranean and Atlantic coasts in three
successive principal phases (Fig. 5). Their expansion coincided
with other social and economic changes of Neolithic and Copper
Age societies beyond the scope of this article. The older gener-
ation of archaeologists were correct concerning a maritime dif-
fusion of the megalithic concept. They were wrong regarding the
region of origin and the direction of the megalithic diffusion. The
megalithic movements must have been powerful to spread with
such rapidity at the different phases, and the maritime skills,
knowledge, and technology of these societies must have been
much more developed than hitherto presumed. This prompts a
radical reassessment of the megalithic horizons and invites the
opening of a new scientific debate regarding the maritime mo-
bility and organization of Neolithic societies, the nature of these
interactions through time, and the rise of seafaring.
3971-3805 cal BC
(3960-3880 cal BC)
4295-3495 cal BC
(3800-3560 cal BC)
3885-3440 cal BC
(3715-3530 cal BC)
~4200–3600 cal BC
3013-2626 ca BC
(2918-2696 cal BC)
3504-3349 cal BC
3409-3364 cal BC
3635-3112 cal BC
3619-3351 cal BC
3400-3050 cal BC
3121–2619 cal BC
3030–2704 cal BC
1913-1692 cal BC
(1878-1753) cal BC
4503–4103 cal BC
(4432–4233 cal BC)
4371–4263 cal BC
(4358–4275 cal BC)
~1800-1200 cal BC
~3500-2900 cal BC
3463-2913cal BC
(3153-2930 cal BC)
3961-3432 cal BC
(3943-3500 cal BC)
2472-839 cal BC
(2441- 1306 cal BC)
3844-3383 cal BC
(3658-3432 cal BC)
3743-3521 cal BC
(3673-3567 cal BC)
3883-3782 cal BC
3837-3796 cal BC
3500-3300 cal BC
3944-3638 cal BC
(3796-3652 cal BC)
3475-3417 cal BC
(3462-3432 cal BC)
4327−4266 cal BC
(4302−4273 cal BC)
Fig. 4. Map showing dates estimated for the start of accessible megaliths as dolmens and passage graves in the different European regions, with 95%
probability (68% probability in brackets). Italic bold type is used for date ranges of the posterior density estimates based on samples from accessible
megalithic graves, regular bold type is used for simple calibrated radiocarbon dates from accessible megalithic graves, and regular italic type is used for the
probabilities of the posterior density estimates associated with the earliest cultural material in dolmen or passage graves.
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ACKNOWLEDGMENTS. I thank members of the AMS facilities in Trondheim
(Norwegian University of Technology and Science) Marie-Josée Nadeau
and Pieter Grootes, Johannes Müller (Kiel University, Germany), Kristian
Kristiansen (University of Gothenburg, Sweden), John Koch (University of
Wales, United Kingdom), and Jonathan Horwitz (Åsbacka, Sweden) for
critical feedback on the work. This project received funding from the
graduate school Human Development in Landscapes, Kiel, Germany, and
the European Union’s Horizon 2020 research and innovation program un-
der the Marie Sklodowska-Curie Grant Agreement 706034. The content of
this study does not reflect the official opinion of the European Union.
Responsibility for the information and views expressed in the report lies
entirely with the author.
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