Among the ruins of ancient cities scattered across northeastern Spain, archaeologists have uncovered a grisly yet fascinating relic of the past: severed human skulls, pierced with iron nails, displayed for all to see.

Who did these remains belong to? Were they revered ancestors, vanquished enemies, or something else entirely? A new study used cutting-edge science to piece together their stories.

Well-traveled Skulls

The research focuses on two key sites: Puig Castellar, near Barcelona, and Ullastret, in the province of Girona. Both locations were once bustling hubs of Iron Age life, where communities thrived, traded, and sometimes clashed. 

Researchers in Spain analyzed the skulls using a technique called isotope analysis. By examining the ratios of certain elements in tooth enamel, they could determine where these individuals lived and moved to during their lives. Teeth, unlike bones, lock in chemical signatures from childhood, acting as a kind of geological time capsule.

In particular, two isotopes were important for this research: strontium and oxygen. Strontium isotopes vary depending on the local geology, while oxygen isotopes reflect the climate and water sources of a region. Together, these elements can reveal whether someone grew up locally or traveled from afar.

At Puig Castellar, only one of the four individuals studied had a chemical signature matching the local area. The other three appeared to have come from regions with different geological profiles. This suggests that they were not native to the settlement. At Ullastret, the picture was more mixed. Two of the three individuals seemed to have lived locally, while the third had a non-local signature.

A Ritual of Power and Reverence

“Our premise in approaching the study was that if they were war trophies, they would not come from the sites analysed, while if they were venerated individuals, these would most likely be local”, explains Rubén de la Fuente-Seoane, archaeologist at the Autonomous University of Barcelona and first author of the study.

“Our results reveal that the individuals from Puig Castellar and Ullastret would not have been randomly selected. There would have been a homogeneous trend towards men in these rituals. However, the mobility and localization patterns suggest a greater diversity, which could also imply social and cultural differences among the individuals of the two communities,” he added.

So it sounds unlikely that all severed heads were war trophies from distant enemies. Some of these individuals may have been locals, possibly important figures in their communities. At Puig Castellar, the skulls were found exposed near the settlement’s walls, suggesting they were displayed prominently, perhaps as a warning or a symbol of power. At Ullastret, the heads were discovered in domestic areas, hinting at a more intimate, possibly ritualistic context, displayed on a wall or doorway of adjacent houses.

Yes, it sounds confusing, but it can’t be ruled out that the nailed heads served a dual purpose: to intimidate enemies and to venerate ancestors.

As de la Fuente-Seoane cautions, this study is just the beginning. “Our study is a first approach to this archaeological problem using a method that is revolutionizing the way we study mobility in the past,” he said. “At the same time, it suggests that the selection of individuals for the severed heads ritual was more complex than initially thought.”

A Window into Iron Age Life

The findings also align with historical accounts from Greek and Roman writers, who described similar practices among the Gauls and Iberian mercenaries. These ancient authors wrote of enemies’ heads being impaled on spears or stored in boxes, suggesting that such rituals were widespread in Iron Age Europe.

During this period, from the 6th to the 1st century BCE, the region was undergoing significant changes. The arrival of Mediterranean traders, including Phoenicians and Greeks, brought new goods, ideas, and conflicts. Local societies became more hierarchical, with powerful elites controlling resources and territory.

 The isotopic data from animal remains suggest that livestock, particularly cattle, were moved across larger territories, possibly for trade or seasonal grazing. This mobility may have extended to people as well, with individuals traveling between settlements for trade, marriage, or other reasons.

The researchers hope to expand their work by analyzing more remains and incorporating DNA studies. This could reveal genetic ties between individuals and shed light on their origins and relationships.

For now, the severed heads of Puig Castellar and Ullastret remain enigmatic. But thanks to the power of modern science, we are one step closer to understanding the lives and deaths of these ancient people. 

The findings appeared in the Journal of Archaeological Science: Reports.