Archeological evidence hints that during the Iron Age, almost all of Western Europe was at war. Hundreds of Iron Age weapons that belonged to the Celts have been unearthed from ancient settlements — as well as hundreds of human bones dated to the same period. In a recent study, scientists set out to fact-check a bloody, pervasive tale from this time: According to ancient Greek authors who passed through what was then Gaul, the Celts weren’t just a warring people — they were a people with a penchant for beheading.

A team of French researchers writes in the Journal of Archeological Science that Classical texts document the practice of the Celts cutting off their enemies’ head post-battle, tying those decapitate heads around their horses’ necks, and transporting the gruesome cargo to their settlements. Additionally, in Provence, a region in southwestern France that borders Italy, archaeologists have found statues that represent these warriors transporting their haul. In other places in southern France, archeologists have discovered human skulls with iron nails in them and stakes fitted to house a human skull.

So it seems pretty obvious that the Celtic tribes who lived in Gaul — an area that now encompasses present-day France, Luxembourg, Belgium, northern Italy, and most of Switzerland — were fans of a good beheading. But what hasn’t been verified scientifically was if anything happened to these heads after they were severed: Greek writers named Strabo and Diodorus wrote that they saw heads embalmed with cedar oils, but this hasn’t been confirmed by modern researchers. The new research brings the picture into clearer focus, providing the first evidence of exactly how the Celts prepared their war trophies.

Cranial fragments examined in this study. Ghezal et. al.

Embalming, while an involved process, would have stood to benefit the Celts bringing their trophies home. They wanted to show off their kills, sure, but they also didn’t want those kills to stink up the neighborhood.

To explore this issue, the scientists set off to an archeological settlement excavation site in Le Cailar, which served as an important port during the Iron Age. It’s situated at a wide lagoon connected to the Rhône River, and it was occupied by the Celts from the 6th century BC until the Romans took over Gaul in the 1st century AD. Here, weapons and human skulls found near what was once the settlement’s walls indicate that the gates to Le Cailar once bore a display of human heads — a warning to enemies, and a sign of victory.

Overall, 2,700 fragments of human bones and skulls have been found here — and many of these skulls contain cut marks that go beyond decapitation. The study authors write that these cut marks indicate that the heads were prepared for display “by the removal of cervical vertebrae and aperture of the postero-inferior portion of the cranium, probably — to remove the brain; and tongue ablation, or at least the scraping of the muscles under the mandible.”

Maps of the Le Cailar excavation, with the distribution of each type of remains and location of samples. Ghezal, et. al.

Here, the scientists focused on eleven cranial fragments for special chemical analysis. And just as the Greek texts hinted, the chemicals they detected on these bones indicate that the heads indeed went through an embalming process. The team found the presence of saturated and unsaturated fatty acids — indicative of the use of animal fats — as well as monoacylglycerols, sterols, alkanes, alkanols, and biomarkers of conifer resins. These chemicals reveal that the heads were treated with a mixture of resins and plant oils. A conifer, for example, is a type of evergreen tree — like a cedar, for instance.

“The use of a mixture of resin and plant oil is documented, in many societies and at different periods in antiquity, for their antibacterial, anti-oxidative, and aromatic properties,” the scientists write.

The short-term advantage of this mixture was that it likely made the heads stink less. The long-term advantage was that it contained anti-bacterial properties that kept the head from rotting as quickly.

Strabo, one of the Greeks who passed by, wrote that the Celts “never gave back the head belonging to the most famous and brave person, even for an equal weight in gold.” This means that you would have been able to know who a severed head belonged to when you passed by Le Cailar — because, if anything, in Gaul you could get a head embalmed right.