Our ancient ancestors have done some interesting things to human bones over the years, but one example from the Iron Age Iberian Peninsula is a real puzzle.
There, in multiple locations, archaeologists have turned up a number of human skulls, removed from their skeletons, and some with large iron spikes or nails driven right through the forehead, and protruding out through the occipital bone in the back of the head.
What was the reason for this practice? Many previous studies suggest that the primary motivation was the display of war trophies, in which the heads of one’s enemies were nailed to a wall.
But there’s another possibility: that the heads belonged to venerated community members, and the display was a way of honoring them after death.
Now, new isotope analysis of skulls found at the archaeological sites of Ullastret and Puig Castellar suggests that both interpretations might be true.
“Who were these individuals and for what were their heads used?” says archaeologist Rubén de la Fuente-Seoane of the Autonomous University of Barcelona, who led the research.
“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.”
The research focused on the skulls of seven men, either with nails, or holes where nails had been driven, from both sites in the first millennium BCE – four from Puig Castellar and three from Ullastret.
The researchers performed strontium and oxygen isotope analysis on enamel from the teeth of these skulls, and the skulls of animals that had also been found in the regions from the same time periods.
Strontium and oxygen isotopes enter the body through food and drink, respectively, and replace some of the calcium in our teeth and bones. The interesting thing about this is that the ratios of these isotopes vary regionally, and your body retains them for your lifespan.
Archaeologists can look at specific isotopes and determine not just how a person ate, but where they lived, and how they moved about over the course of their lifetime.
The team’s research confirms that the skulls were deliberately chosen; but the reason for those choices, and the reasons for the ritual display of the skulls, were probably multiple.
“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. In contrast, Ullastret revealed a mixture of local and non-local origins,” Fuente-Seoane says.
“This result suggests that the practice of severed heads was applied in a different way at each site, which seems to rule out a homogeneous symbolic expression. But more research is needed to be sure.”
The skulls at Puig Castellar were likely, the researchers found, war trophies, displayed on external city walls or the city gate to intimidate outsiders and possibly locals, too. Two of the skulls at Ullastret, on the other hand, were of local origin, and found in the street in the middle of the city, suggesting that their emplacement was for the benefit of the people who lived there.
Only one of the Ullastret skulls was placed on the city wall – the skull of a non-local man. That skull could have been a war trophy.
The animal teeth provided a reference point for the skulls, but also revealed the different approaches to resource management, and the mobility patterns for both the humans and animals in each city. These differences may be attributed to differences in cultural values, the researchers say – which, in turn, could play a role in the display of severed heads.
“This differentiation reflects a dynamic and complex society with important local and external interactions. Our study is a first approach to this archaeological problem using a method that is revolutionizing the way we study mobility in the past,” Fuente-Seoane explains.
“At the same time, it suggests that the selection of individuals for the severed heads ritual was more complex than initially thought.”
As with many practices of the ancient past, it will be extremely difficult, if not impossible, to ascertain the reasons behind why the Iberians decorated with skulls nailed to walls. But, as with many things we humans do, it seems even more possible than ever that there’s no simple, singular explanation.
The team’s research has been published in the Journal of Archaeological Science: Reports.
