Brittany burial mounds may hide human-shaped stones as Coëby cemetery mystery deepens
For archaeologists, the Coëby cemetery in Brittany, France, is a gold mine for research. It contains several prehistoric stone monuments and earth mounds. In a new study of two unusually large mounds, scientists may have stumbled upon a rare style of funerary monument.
Earthen giants
The elongated earthen barrows, known as TRED30 and TRED31, are 50–80 meters (164–262 feet) long and up to 1.8 meters (5.9 feet) high. They were first discovered in 1986 and haven't been fully excavated. Because they are fragile and have protected status, teams can't just dig them up to see what, if any, secrets they may hide.
In new research published in the journal Archaeological Prospection, scientists from the French National Center for Scientific Research (CNRS) surveyed the two mounds in 2020 using electrical resistivity mapping.
This noninvasive technique involves inserting small metal stakes into the ground to pass a safe electrical current through the earth. By measuring how easily the current travels, scientists can map what is hidden below the surface, as soil conducts electricity while solid stone resists it.
Clues from the past
Their surveys revealed resistance spikes in the centers of both mounds. The signatures matched the electrical profile of granite blocks previously measured at nearby dolmens (ancient megalithic tombs). "These resistant anomalies indicate the very likely presence of stone clusters within TRED30 and TRED31 barrows," wrote the researchers in their paper.
In TRED30, the spikes became stronger when scanning deeper, indicating that substantial stone structures are buried deep within the core of the monument. Meanwhile, the results from TRED31 showed evidence of buried stone structures close to the surface. Years of erosion had exposed the tip of one stone block, although this had previously gone unnoticed.
While the scans cannot reveal the exact layout of these buried features or what their purpose may have been, the study authors have some ideas. Based on previous digs at another mound in the same cemetery, the large structures may be rough, human-shaped standing stones.
These could be similar to Passy-type monuments found elsewhere in France, where long earthen burial mounds covered standing stones or other funerary structures. "It therefore seems reasonable to confirm that these two barrows are indeed funerary monuments belonging to the Coëby cemetery."
While the researchers want to study the mounds in more detail, they say that only a complete excavation will reveal exactly what lies beneath.
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More information
Philippe Gouézin et al, Atypical Long Barrows in the Cöeby Neolithic Cemetery (Trédion, Morbihan, France)? The Contribution of Electrical Surveys, Archaeological Prospection (2026). DOI: 10.1002/arp.70060
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Citation: Brittany burial mounds may hide human-shaped stones as Coëby cemetery mystery deepens (2026, August 1) retrieved 1 August 2026 from https://phys.org/news/2026-07-brittany-burial-mounds-human-stones.html
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