Top image: The famous neolithic menhirs near Carnac, consisting of alignments, dolmens, tumuli and single menhirs – more than 3,000 in total.  

For aeons, Brittany's stone arrangement at Carnac has provided an important window into Europe's prehistory, vying with the Stonehenge and Malta's temples for imagination. Like its counterparts, its purpose and chronology have remained a mystery – until now. A new study, under which a rescue excavation was carried out, has identified preserved foundation pits of standing stones, encircling a monumental tomb and several cooking pits.

This amazing find is the result of a rescue excavation at Le Plasker, a hitherto unknown part of the massive Carnac complex. Directed by Archeodunum's and the University of Gothenburg's Audrey Blanchard, the excavation was a dash for time, undertaken before a 7,000 square meter business park can be built on the site in the center of Plouharnel. They’ve published their finds in the latest edition of the journal  Antiquity.

The collaboration is a Frenco-Swedish one, under the aegis of the ERC-funded NEOSEA research project. Together, they’ve accurately dated the famed alignments, shedding light on the mystery of Carnac. Covering more than ten kilometers from Carnac/La Trinité-sur-Mer to Erdeven, the Carnac complex has more than 3,000 standing stones – a one-of-a-kind megalithic fabric!

Sifting Through Organic Remains, Employing the Bayesian Model

Archaeological work in Brittany's alkaline soils has been plagued for years by the limited preservation of organic remains, especially bone, rendering standard radiocarbon dating a consistent struggle.

Earlier excavations, while groundbreaking, did not always result in the fine detail required for accurate dating. But the Le Plasker team utilized advanced contemporary excavation methods and systematic sampling on a strict regimen.

Dolmen de Cruz-Moquen, Christianised before 1823, situated on to the road between the church of Carnac and the megalithic alignements of "Le Ménec". This postcard is sometime before 1903.

The researchers employed a robust statistical technique: Bayesian modelling of an unprecedented chain of radiocarbon dates. Carefully sampling charcoal from short-lived trees – such as hazel and oak sapwood – from the untouched, lower parts of features like a circular ditch, a tomb cist, and even the foundation pits of the standing stones, they acquired forty-nine new radiocarbon dates.

This comprehensive dataset is one of the most comprehensive and richest radiocarbon sequences ever compiled for western France, enabling them to define a high-precision chronology for the site – a dynamic construction history evolving over three centuries in the Middle Neolithic.

“The alignments in the Carnac region now appear to be among the earliest megalithic monuments in Europe, with this section constructed between 4600 and 4300 cal BC. We have also confirmed the Bay of Morbihan as the earliest megalithic region in Europe,” says archaeologist Bettina Schulz Paulsson at the University of Gothenburg, who leads the NEOSEA project and is one of the researchers behind the new study, in a press release.

Le Plasker's Story: From Mesolithic Origins to Monumental Stone Rows

The history of the site begins much earlier than anticipated, with Late Mesolithic occupation evidenced from 5700–5100 BC. Signs of a potential hut, with an oval ditch and even possible small standing stones, suggest that the importance of the site lasted through the centuries.

Following an interval, the site was dramatically reused with the development of a pre-megalithic monumental tomb in about 4700 BC. This distinctive funerary architecture, a small circular tumulus enclosing a quadrangular dry-stone cist, is one of the earliest such instances in Europe, a seminal step from the previous pit burial tradition to the later, much larger megalithic tombs, reports

It was ringed by forty-six unworked monoliths, transported kilometres and deliberately positioned to replicate a natural rocky terrain – an intentional alteration of the environment, possibly intended to recall the craggy granite escarpments whence these rocks came. Two large cooking pits, discovered in the vicinity, imply on-site, contemporaneous activity.

Subsequently, not much later, or more likely simultaneously with the construction of the tomb, the mythical alignments of standing stones arose between 4670 and 4250 BC. Although the gigantic upright stones themselves no longer exist – probably dismantled and recycled in antiquity, maybe even reused in subsequent Neolithic tombs – their enormous foundation pits remain. These pits, which include one with an average diameter of 1.8 meters (5.9 feet) and which contains more than sixty large granite slabs (over 100 kg each), are a story of careful planning and considerable uprights, possibly over three meters high.

Audrey Blanchard (Archeodonum) and Jean Noel Guyodo, University of Nantes, during the excavation of Le Plasker.

Fascinatingly enough, cooking pits were found in close proximity to, and even parallel with, these stone foundations. Although their precise use remains under exploration, charcoal analysis has eliminated grain smoking or roasting, tending strongly toward the belief that these were cooking areas, possibly for communal feasting rituals for the extraordinary effort of putting these enormities in place. Envision the parties, the communal meals, as these gigantic edifices gradually began to form!

A Living and Dynamic Landscape

The Le Plasker results conclusively show that the formation of the Carnac megalithic landscape was not a single, instantaneous process, but a multifaceted, dynamic enterprise evolving in a series of clearly differentiated steps over at least three centuries.

New standing stones and alignments were incrementally added over time, always faithfully respecting and recreating an initial model, proving an extraordinary continuity in social traditions and symbolism.

 “Thanks to nearly 50 radiocarbon dates and the application of Bayesian statistical modelling, we were able to reconstruct the site’s history with unprecedented chronological precision,” concluded Paulson.