Conflict has existed throughout human history, and it has often been violent. Attacks, assassinations, raids, ambushes and vendettas feature in archaeological records almost as far back as the origin of humankind itself. But not war.

    War – as opposed to conflict – requires organisation, be it temporary or permanent. This usually involves the creation of institutionalised armies belonging to at least one of the groups involved. War legitimises violence, meaning one person can kill another without it being considered murder. War is also temporary by nature, usually lasting for a period of months or years.

    Various studies suggest a connection between the birth of war and human settlement, when control of land and property became increasingly important.

    The emergence of surpluses during the Neolithic era, especially in agriculture and livestock, soon led to concentrated power, permanent inequality, and the desire to expand and defend territories. It also led to the establishment of the first states, which maintained, expanded and consolidated power by recruiting large armies to wage war as we understand it today.

    The birth of war

    To trace the emergence of warfare, prehistorians and archaeologists have long been forced to rely on indirect indicators. These include defences, recorded appearances of weapons, or the identification of certain graphic elements, such as cave paintings. More recently, research has shifted towards direct evidence, particularly wounds on human bones, which are arguably the most incontrovertible evidence we have of past violence.

    Thanks to advances in forensic anthropology, we have learned that the vast majority of known mass burial sites with signs of violence in European prehistory until well into the Neolithic era (6000-3000 BC) were essentially massacres. These were indiscriminate killings of communities of no more than 20-30 people, including whole populations of men, women and children, as a result of brutal surprise attacks by other groups.

    The few archaeological sites that do not fit into this category appear to be the result of sacrifices or other violent ritual practices.

    At sites such as the British settlements of Crickley Hill and Hambledon Hill, the discovery of hundreds of arrow heads around defences might suggest large coordinated attacks, but there is little to no skeletal evidence that they had actually been used in battle. For this, one would have to wait until the Bronze Age, around 1200 BC and the Battle of Tollense in Germany.

    San Juan ante Portam Latinam: broken bones and paradigms

    The burial site at San Juan ante Portam Latinam (SJAPL) was discovered in 1985 in Laguardia (Álava, Spain), and was excavated by J. I. Vegas and his collaborators 1990 and 1991. The skeletal remains of at least 338 people were found there, which were dated to around 3200 BC, in the late Neolithic period.

    Initial studies found evidence of violence. Specifically, there were 53 head injuries and eight arrowhead wounds that had occurred some time before death (antemortem), and had already healed. However, there were also five arrowhead wounds and one head injury that had occurred around the time of death (perimortem), and had not healed.

    Furthermore, it was suspected that the 52 flint arrowheads found in isolation (most with signs of impact) had been stuck in the bodies buried there, and had not been deliberately buried with them. Therefore, despite the apparently limited number of unhealed wounds, the burial site was originally thought to be the result of a massacre, possibly because of the lack of known prehistoric sites with signs of collective violence at the time.

    Previous study on European Neolithic sites with evidence of violence soon made the uniqueness of SJAPL clear. While perimortem trauma, especially cranial trauma that is typical of melee combat, predominated at other sites, arrowhead wounds – evidence of combat at a distance – and antemortem trauma seemed to predominate at SJAPL. This suggested a longer, more complex and less lethal conflict.

    The demographic at the site is also different from others. While at other sites there were men, women and children, there were predominantly adolescent or adult males at SJAPL.

    Reexamining the remains

    Recently, we have reexamined the remains found at SJAPL to assess its singular, anomalous results. This review identified a total of 107 head injuries, of which 48 were unhealed and 59 healed, and a total of 47 injuries to other parts of the skeleton, of which 17 were unhealed and 30 healed.

    Interestingly, the vast majority involved adolescent and adult males, particularly those that were unhealed. In addition, some of these men were found to have both healed and unhealed wounds, indicating that they had been exposed to violence on several occasions.