Archaeologists have been investigating human bones found near the ruins of a bridge in the Three Lakes region of Switzerland. They aim to not only uncover what happened but also to better understand the Celtic heritage of the region.

A mix of bones, skulls, and wooden beams recovered from a riverbed raises questions. What happened, and who were these individuals found there?

The ruins of the Celtic bridge at Cornaux/Les Sauges and the twenty skeletons found nearby have been a subject of speculation since their discovery in 1965 during renovations of the Thielle Canal.

Specialists in archaeology, anthropology, thanatology, biochemistry, and genetics have revisited the case. Their study, supported by the Swiss National Science Foundation (SNSF) and the Autonomous Province of Bolzano, was recently published in Scientific Reports.

The Sudden Accident Theory Dominates

This study is part of an international project led by the University of Bern and the Eurac Institute for Mummy Studies in Bolzano, aiming to improve our understanding of the Celts in Switzerland and Northern Italy. The predominantly oral culture of the Celts has left limited written sources, and much of what is available comes from Julius Caesar’s writings. These are the accounts of a military adversary, so they are not necessarily objective and complete, says Zita Laffranchi, a postdoctoral researcher at the Institute of Forensic Medicine at the University of Bern.

By focusing on archaeological findings, we can give a voice to people who are not documented in the written record. Along with her colleagues, Laffranchi conducted a bioarchaeological investigation to try to reconstruct the events at Cornaux/Les Sauges.

The Celtic bridge ruins and skeletons are indeed controversial. For some, a sudden flood or tsunami caused the collapse of the wooden structure. For others, the bodies were victims of human sacrifice, a Celtic practice often associated with water. The skeletons were examined from all angles to try to reconstruct the circumstances of the drama. Their state of preservation and the notable presence of brain fragments in five of the skulls suggest that sediment covered the bodies soon after death. The remains show multiple bone injuries distributed throughout the bodies, from the skulls to the legs, appearing to have been caused by violent impact.

Cornaux/Les Sauges: geographic position and archaeological plan. (a) geographic position of Cornaux/Les Sauges and simplified geological map of the surrounding areas; (b) archaeological plan of the site with colors indicating the dendrochronological dates for some of the wood beams, and (c) picture of COR-16 in situ
Cornaux/Les Sauges: geographic position and archaeological plan. (a) geographic position of Cornaux/Les Sauges and simplified geological map of the surrounding areas; (b) archaeological plan of the site with colors indicating the dendrochronological dates for some of the wood beams, and (c) picture of COR-16 in situ. Credit: Zita Laffranchi et al. / Laténium—Archaeology Park and Museum Neuchâtel

No intentional or sharp object-induced wounds were identified, unlike the findings at other European sites where sacrifices are documented. These elements, plus the fact that some bones were entangled with pieces of wood, point to an accidental event. The theory that a tsunami caused the bridge collapse, therefore, seems likely.

Possible Multiple Waves of Deaths

This is not the only information the skeletons have provided. Some bones and teeth were also subjected to chemical analyses. Radiocarbon dating can provide a range of dates to understand when an individual lived, while other isotopic analyses can provide information about the diet and places of residence of the victims. Finally, paleogenetic analyses allowed the research team to analyze the ancient DNA of half the individuals.

After making the bones speak in this way, scientists confirmed the presence of at least 20 people, with no apparent familial links: a girl, two other children, and 17 adults—mostly young, and 15 of whom seem to have been men. This clear demographic bias, with a strong majority of young adult males, could correspond to a group of prisoners or slaves who were sacrificed or a convoy of merchants or soldiers.

Finally, since some radiocarbon dates have proven ambiguous, it is impossible to be sure that all deaths occurred simultaneously and coincided with the bridge’s destruction. Considering all these elements, it is very likely that a sudden, violent accident occurred in Cornaux, summarizes Marco Milella, a researcher at the University of Bern and co-leader of this project. But this bridge had a prior life. It may have been a place of sacrifice, and some bodies could have preceded the accident. There is no reason to choose between the two alternatives.

The exact sequence of events at the Celtic bridge in Cornaux/Les Sauges is likely to remain a mystery. In this kind of research, we are interested in individuals. We trace their life stories, which can be emotional, says Laffranchi. But ultimately, the goal is to better understand our cultural and biological heritage at the population level.

At the Heart of Celtic Europe

The Three Lakes region was important for the Celts, especially the Helvetii, the largest Celtic tribe that settled in the area between Lake Geneva and Lake Constance. This new study, the first to use paleogenomics for analyzing Celtic individuals in Switzerland, confirms their genetic proximity to other Iron Age populations.

For instance, some lineages identified in Cornaux have been found in Britain, the Czech Republic, Spain, and central Italy. Isotopic analyses indicate that some individuals may have grown up in the Three Lakes region and others in the Alps.

These discoveries confirm the region’s importance at that time and support the increasingly grounded notion of a mixed population and high mobility among Celtic groups. Far from being isolated by the surrounding mountains, our Helvetian ancestors already lived in a busy crossroads in the heart of Europe.


Swiss National Science Foundation | Laffranchi, Z., Zingale, S., Indra, L. et al. Geographic origin, ancestry, and death circumstances at the Cornaux/Les Sauges Iron Age bridge, Switzerland. Sci Rep 14, 12180 (2024).

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