The Carnac alignments
Around Carnac in southern Brittany, rows of standing stones run for kilometres across the land between the Bay of Quiberon and the Gulf of Morbihan. With tombs, mounds, stone enclosures and Europe's highest reported density of Alpine greenstone artefacts, they form one of the richest megalithic landscapes in Europe, extending more than 10 km from La Trinité-sur-Mer to Erdeven[1]. In July 2025 the Megaliths of Carnac and of the shores of Morbihan were inscribed as a World Heritage property, with monuments dated from about 5000 to 2300 BCE[2].
The rows themselves had resisted dating. The soils are acid and destroy bone, the main excavations happened in the 19th and early 20th centuries with patchy records, and the visible rows have hardly been dug since Zacharie Le Rouzic in the 1920s and Werner Hülle in 1940 to 1942[1][3]. Across Europe, Bayesian models of 2,410 radiocarbon dates place the first megaliths in north-west France in the first half of the fifth millennium BC, but those dates come from tombs[4].
In 2020 a rescue excavation at Le Plasker in Plouharnel, 2 km west of the Le Ménec rows, found the foundation pits of a lost section of the complex. Forty-nine radiocarbon dates on short-lived charcoal show a Late Mesolithic hut about 5700 cal BC, a small mound over a stone cist about 4790 to 4640 cal BC, and rows of standing stones raised in stages between about 4670 and 4250 cal BC beside cooking pits[1]. Of the 4 questions on this site, 0 are answered. The most likely answer to “When were the Carnac rows raised?”, not yet confirmed: the rows were raised in the fifth millennium BC, from about 4670 to 4250 cal BC, in stages over about three….
Key questionsset by the editors
The site
The surviving rows, such as Le Ménec, Kermario and Kerlescan, run roughly parallel across low ground and are associated with standing-stone enclosures[1]. The Thoms surveyed them with instruments in the early 1970s and published plans that remain the most detailed measured record[5][6]. The complex was larger than what stands now: stones were broken and reused in later tombs, and others have been removed in recent times[7][1].
In June 2023 about 39 small fallen menhirs at Montaubin, outside the protected area, were destroyed to build a DIY store; the regional heritage service judged that perhaps four had archaeological value, and prosecutors opened an investigation[8]. The episode shows how much of the complex survives only as low, unrecorded stones and buried pits.
Timeline
What was found
Le Plasker covers about 7000 m² on a south-west-facing slope overlooking the sea. The earliest feature is an oval ditched structure of about 5.7 by 5.1 m, read as a Late Mesolithic hut, with three small monoliths beside it[1].
About 300 years later a mound 3.3 m across was built directly over the hut, covering a dry-stone cist of 0.7 by 0.9 m with no surviving bones. Forty-six unworked granite boulders, brought from more than 2 km away and laid with their weathered faces up, surround its southern side, as if to recreate a natural outcrop[1].
To the west, foundation pits about 1.8 m across, each packed with some 60 wedging blocks, held standing stones that the authors estimate stood more than 3 m tall. The stones themselves are gone, removed in an orderly way that left the wedges in place. Cooking pits with charred stones, about 1.5 m across, lie beside and in line with them[1].
What is known
The Bayesian model gives six phases: Mesolithic occupation 5699–5621 cal BC and 5563–5075 cal BC; the mound and cist 4791–4640 cal BC; the main alignments 4668–4368 cal BC; a last standing stone 4372–4249 cal BC; and last cooking pits 4251–4040 cal BC, all at 95.4% probability. The model agreement indices are Amodel 105 and Aoverall 98.7[1].
The rows were not built at once. New stones and rows were added along the same north-north-west to south-south-east axis over about three centuries, so a row is the outcome of many acts of building, not a single plan executed in one go[1].
The Le Plasker dates fall in the same centuries as the earliest Carnac tombs and the large mounds such as Saint-Michel and Tumiac, and early in the European sequence of megaliths[1][4]. The 2019 European database holds 177 dates from Brittany, none of them from a stone row, which is why Le Plasker matters[4].
The explanations
The astronomical reading treats the rows and large menhirs as instruments: Alexander and Archibald Thom argued that the Carnac stones were laid out to observe the extreme rising and setting points of the moon, with the great menhirs as foresights[9][10]. It predicts row directions and sightlines that match lunar and solar horizon events at the date of building, better than chance.
The landscape reading holds that the rows translated the region's natural granite outcrops and ridges into a built form, with boulder sizes graded to the slope and stones placed to echo the original rock landscape[11][1]. It predicts that row positions follow topography and outcrops more closely than the sky.
The communal-project reading, which the Le Plasker team favours, sees the rows as a monument built and rebuilt over generations, with fires and probably feasts at the stones when people gathered to raise them; the cooking pits are the evidence, though their use is not yet proved[1]. It predicts staggered dates along each row and food residues in the pits.
These readings can overlap; what the evidence can test is which one predicts the layout and the sequence.
Published claims
| Year | Who | Claimed | Status | Reason |
|---|---|---|---|---|
| 1805 | Jacques Cambry[13] | The Carnac rows are a temple of the Celts, raised for the druids' cult of stones. | Ruled out | Radiocarbon dates put the raising of the stones at Le Plasker in the fifth millennium BC, thousands of years before any Celts or druids[1] |
| 1971 | Alexander and Archibald Thom[9] | The large Carnac menhirs, the Grand Menhir Brisé above all, were foresights for marking the moon's extreme rising and setting points. | Disputed | A field re-examination of the sight-lines cast serious doubt on the lunar reading[14] |
| 1972 | Alexander and Archibald Thom[5] | The Le Ménec and Kermario rows were laid out to a geometric plan in a standard unit, the megalithic yard. | Disputed | The unit and method are widely criticised, and at Le Plasker the rows grew by additions over three centuries rather than to one plan[1] |
| 1976 | Alexander and Archibald Thom[10] | The rows at Le Ménec and Kermario served as two lunar observatories, with the stone rows used to extrapolate the moon's positions. | Disputed | The field evidence behind it was re-examined and found wanting, though no orientation test against random lines has been published[14] |
| 1981 | Evan Hadingham[14] | The field evidence for a lunar observatory at Carnac does not hold up when re-examined on the ground. | Most likely | No later study has revived the Thoms' Carnac observatory, and the staged growth of the Le Plasker rows fits a monument added to over generations[1] |
| 2008 | Emmanuel Mens[7] | Standing stones in western France were broken up and reused in later monuments, which refitting of the fragments shows. | Accepted | Refits of fragments across monuments demonstrate it, and the emptied foundation pits at Le Plasker show stones removed wholesale[7][1] |
| 2011 | Chris Scarre[11] | The rows turn the region's natural granite outcrops and ridges into a built landscape. | Still possible | Unworked boulders laid face-up like an outcrop at Le Plasker fit it, but it has not been tested against other readings[1] |
| 2019 | Bettina Schulz Paulsson[4] | Megalith building began in north-west France in the fifth millennium BC and spread along the coasts of Europe by sea. | Still possible | It rests on a model of 2,410 radiocarbon dates, none of them from a Breton stone row, so it frames the rows without dating them[4] |
| 2025 | Audrey Blanchard and colleagues[1] | The Le Plasker rows were raised in stages between about 4670 and 4250 cal BC, beside a mound and cooking pits. | Accepted | Forty-nine dates on short-lived charcoal in a modelled sequence support it, though the main surviving rows are not yet dated the same way[1] |
| 2025 | UNESCO World Heritage Committee[2] | The megaliths of Carnac and the Morbihan shore form one monumental landscape built between about 5000 and 2300 BC. | Accepted | The inscription rests on the State party's nomination and the advisory body's evaluation, and no one disputes the date range[2] |
| 2026 | Guillaume Bruniaux and colleagues[3] | Buried structures around the Carnac rows, such as pits, hearths and fallen stones invisible at the surface, can be found with combined geophysical methods. | Still possible | Only the first results of the 2024 surveys are published, and none of the anomalies has yet been excavated[3] |
What would settle it
Dates from the standing rows themselves. Le Plasker shows that foundation pits with wedging stones and charcoal survive and can be dated; similar small excavations at Le Ménec, Kermario and Kerlescan would test whether the famous rows are of the same age and built in the same staged way[1][3]. The lipid, phytolith and environmental DNA analyses announced for the Le Plasker cooking pits will show what was cooked there[1].
The astronomical claims would be tested by an alignment analysis that measures every row from lidar and the Thom plans, computes horizon altitudes for the fifth millennium BC, and compares the result with random orientations of the same rows[12][5].
Questions
0 of 4 questions are answered.
Evidence 18 findings
Artifacts
The films, photos, papers and objects this mystery rests on, each with its own key and its distance from the original.
See also
References
- 1.Blanchard, A., Guyodo, J., Schulz Paulsson, B. et al. 2025. Le Plasker in Plouharnel (fifth millennium cal BC): a newly discovered section of the megalithic complex of Carnac. Antiquity 99(406), 915–934.doicited 41 times hereSRC0D69T3PJ4ZTB
- 2.UNESCO World Heritage Committee 2025. Decision 47 COM 8B.23: Megaliths of Carnac and of the shores of Morbihan (France). UNESCO World Heritage Centre.cited 4 times hereSRC0D69T5WW2KYD
- 3.Bruniaux, G., Mathé, V., Agogué, O. et al. 2026. Multi-Method Geophysical Surveys Between and Around the Kerlescan and the Manio Megalithic Alignments in Carnac (Morbihan, France). Archaeological Prospection 33, 499–517.doicited 7 times hereSRC0D69T5D842FM
- 4.Schulz Paulsson, B. 2019. Radiocarbon dates and Bayesian modeling support maritime diffusion model for megaliths in Europe. Proceedings of the National Academy of Sciences 116, 3460–3465.doicited 4 times hereSRC0D69T3YC3GDJ
- 5.Thom, A., Thom, A. 1972. The Carnac Alignments. Journal for the History of Astronomy 3, 11–26.doicited 9 times hereSRC0D69T4660AKZ
- 6.Thom, A., Thom, A. 1974. The Kermario Alignments. Journal for the History of Astronomy 5, 30–47.doicited 2 times hereSRC0D69T4E007ZM
- 7.Mens, E. 2008. Refitting megaliths in western France. Antiquity 82, 25–36.doicited 3 times hereSRC0D69T5N23TCR
- 8.The Local France 2023. French prosecutors open investigation into destruction of Carnac's prehistoric stones. The Local (France).cited 3 times hereSRC0D69T64P5W1T
- 9.Thom, A., Thom, A. 1971. The Astronomical Significance of the Large Carnac Menhirs. Journal for the History of Astronomy 2, 147–160.doicited 1 time hereSRC0D69T4XM4Y38
- 10.Thom, A., Thom, A., Gorrie, J. 1976. The Two Megalithic Lunar Observatories at Carnac. Journal for the History of Astronomy 7, 11–26.doicited 3 times hereSRC0D69T4NT59NN
- 11.Scarre, C. 2011. The Carnac Landscape. Landscapes of Neolithic Brittany (Oxford University Press), 103–134.doicited 2 times hereSRC0D69T55E5DZX
- 12.Institut national de l'information géographique et forestière (IGN) 2026. Nuages de points LiDAR HD. data.gouv.fr.cited 2 times hereSRC0D69T6CG6A4R
- 13.Cambry, J. 1805. Monumens celtiques, ou recherches sur le culte des pierres, précédées d'une notice sur les Celtes et sur les Druides. Johanneau, Paris.cited 1 time hereSRC0D69T6W46TXA
- 14.Hadingham, E. 1981. The lunar observatory hypothesis at Carnac: a reconsideration. Antiquity 55(213), 35–42.doicited 1 time hereSRC0D69T73Y1WZ7