A re-analysis of more than 300 sets of 5,000-year-old skeletal remains excavated from a site in Spain suggests that many of the individuals may have been casualties of the earliest period of warfare in Europe, occurring over 1,000 years before the previous earliest known larger-scale conflict in the region.

The study, Large-scale violence in Late Neolithic Western Europe based on expanded skeletal evidence from San Juan ante Portam Latinam, published in Scientific Reports, indicates that both the number of injured individuals and the disproportionately high percentage of males affected suggest that the injuries resulted from a period of conflict, potentially lasting at least months.

Conflict during the European Neolithic period (approximately 9,000 to 4,000 years ago) remains poorly understood. Previous research has suggested that conflicts consisted of short raids lasting no more than a few days and involving small groups of up to 20–30 individuals, and it was therefore assumed that early societies lacked the logistical capabilities to support longer, larger-scale conflicts.

The earliest such conflict in Europe was previously thought to have occurred during the Bronze Age (approximately 4,000 to 2,800 years ago).

Teresa Fernández‑Crespo and colleagues re-examined the skeletal remains of 338 individuals for evidence of healed and unhealed injuries. All the remains were from a single mass burial site in a shallow cave in the Rioja Alavesa region of northern Spain, radiocarbon dated to between 5,400 and 5,000 years ago.

52 flint arrowheads had also been discovered at the same site, with previous research finding that 36 of these had minor damage associated with hitting a target.

The researchers found that 23.1% of the individuals had skeletal injuries, with 10.1% having unhealed injuries, substantially higher than estimated injury rates for the time (7–17% and 2–5%, respectively). They also found that 74.1% of the unhealed injuries and 70.0% of the healed injuries had occurred in adolescent or adult males, a significantly higher rate than in females, and a difference not seen in other European Neolithic mass-fatality sites.

The overall injury rate, the higher injury rate for males, and the previously observed damage to the arrowheads suggest that many of the individuals at the burial site were exposed to violence and may have been casualties of conflict.

The relatively high rate of healed injuries suggests that the conflict continued over several months, according to the authors. The reasons for the conflict are unclear, but the researchers speculate on several possible causes, including tension between different cultural groups in the region during the Late Neolithic.

It is possible that the existence, in a context of high population pressure, of different cultural groups with distinct lifeways and funerary practices was a source of tension and competition and, as a result, a major catalyst of lethal violence. Evidence of arrowhead injuries and other skeletal signs of violence (e.g., cranial trauma, parry fractures) in other coeval sites of the region, supports an image of standing and organized violence between rival communities. This, together with skeletal and isotopic evidence compatible with biological stress and malnourishment and with fixed mobility in the region, suggests wider social impacts to an extent that has not previously been seen for the European Neolithic record.

Fernández-Crespo, T., Ordoño, J., Etxeberria, F. et al. Large-scale violence in Late Neolithic Western Europe based on expanded skeletal evidence from San Juan ante Portam Latinam. Sci Rep 13, 17103 (2023). https://doi.org/10.1038/s41598-023-43026-9