In the rugged landscapes of northeastern Iberia, ancient fortresses once stood, their walls bearing silent witness to the turbulent rituals of Iron Age societies. Among the most perplexing of these practices is the display of severed human heads—gruesome relics once nailed to walls or placed near entrances. Were they war trophies, grim warnings to enemies? Or were they revered ancestors, honored in death as a testament to their standing in the community? A new study, published in the Journal of Archaeological Science: Reports, takes a fresh look at these enigmatic skulls, using isotope analysis to track the origins and movements of the individuals whose remains were subjected to this unsettling tradition.
For decades, archaeologists speculated on the meaning of these skulls. Some believed they were the heads of foreign enemies, displayed to assert dominance. Others saw them as a way for Iron Age Iberians to commemorate their own fallen warriors. But without hard evidence—without a way to determine where these individuals had lived and died—the debate remained unresolved. Now, thanks to cutting-edge strontium and oxygen isotope analysis, researchers are beginning to piece together a more nuanced picture.
“The severed heads represent a unique symbolic practice within the Iberian world and offer an exceptional opportunity to analyze these communities,” the authors write. “It has been proposed that they might have been protective relics from ancestors or war trophies of foreign enemies. But these hypotheses have not been tested yet, nor has the relationship of these groups with their territory.”
To uncover the origins of these skulls, researchers analyzed human remains from two major sites: Ullastret and Puig Castellar. By examining the isotopic composition of their tooth enamel—specifically, strontium and oxygen levels—the scientists could determine whether these individuals grew up locally or if they had migrated from other regions.
Strontium, an element absorbed from local bedrock through water and food, leaves a chemical signature in bones and teeth that matches the geology of a person’s childhood home. Oxygen isotopes, meanwhile, can reveal patterns of water consumption, providing additional clues about mobility and climate.
The results were striking: at Puig Castellar, three out of four individuals showed isotopic signatures that did not match the local geology. They were likely outsiders, reinforcing the idea that these skulls could have belonged to captured enemies. But in Ullastret, two of the three analyzed skulls did match the local baseline, suggesting that at least some of the severed heads belonged to community members, possibly venerated ancestors or individuals who had fallen out of favor.
“At Puig Castellar, the isotope values of three of the four individuals differ significantly from the local strontium reference, which suggests that they were probably not from the local community,” explains lead author Rubén de la Fuente-Seoane. “In contrast, Ullastret revealed a mixture of local and non-local origins.”
These findings challenge the assumption that the “nailed heads” ritual served a single, universal purpose. Instead, it seems that different settlements adapted the practice to their own needs. In some cases, it may have been a form of intimidation, meant to discourage rebellion or frighten enemies. In others, it may have been a way of honoring ancestors or reinforcing social cohesion.
The positioning of the skulls offers additional insights into their significance. At Puig Castellar, the heads were prominently displayed near the settlement’s walls—a clear indication of their role in power projection and social control.
“The fact that in Puig Castellar the skulls were exposed in an area such as the wall makes the researchers opt for the hypothesis that the reason for their exposure was aimed at the demonstration of power and coercion, both for internal repression and towards a group outside the community,” the study states.
But in Ullastret, the placement was more varied. Some skulls were displayed near homes or within the city itself, raising the possibility that they belonged to revered community members rather than outsiders. The presence of a single foreign skull at Ullastret suggests that the war trophy tradition still existed but was not the dominant function of the ritual.
These insights paint a picture of a dynamic and complex society—one that used ritualized violence not just to threaten enemies but also to reinforce social order, honor certain individuals, or even define territorial boundaries.
This study represents the first systematic application of isotope analysis to severed heads in Iron Age Iberia. It not only provides direct evidence of human mobility patterns during this period but also highlights the importance of integrating bioarchaeological and isotope data to refine our understanding of past societies.
“This differentiation reflects a dynamic and complex society with important local and external interactions,” the researchers write. “At the same time, it suggests that the selection of individuals for the severed heads ritual was more complex than initially thought.”
While this study answers some questions, it raises many more. Why did Ullastret and Puig Castellar differ in their use of severed heads? Were there specific social or political factors that influenced these choices? And how did these practices compare to similar rituals in neighboring cultures?
Future research, the authors suggest, will involve expanding the isotopic dataset and examining additional archaeological sites to see if these patterns hold true across the broader Iberian world.
The severed heads of Iron Age Iberia were not just macabre relics of a violent past. They were symbols—of power, of memory, of fear, and of belonging. By combining advanced scientific techniques with careful archaeological analysis, researchers are bringing new clarity to these ancient traditions, revealing a world far more complex than we once imagined.
“We have established a local strontium reference based on a rigorous protocol,” the authors conclude, “applying in humans a pioneering methodology in Catalonia that, moreover, serves as a first step towards the creation of a Catalan map of bioavailable strontium.”
With this groundbreaking work, archaeologists have not only deepened our understanding of Iron Age Iberia but also demonstrated the power of modern science to rewrite ancient history.
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López-Onaindia, D., et al. (2024). “Strontium isotope analysis in prehistoric European societies.” Journal of Archaeological Science. DOI: 10.1016/j.jas.2024.105035
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Sanmartí, J., et al. (2023). “The role of ritual violence in Iberian society.” Antiquity. DOI: 10.15184/aqy.2023.15
