Modelling massacres. The agent-based modelling of catastrophic events using skeletal data from archaeological excavations.

This article describes the agent-based modelling of catastrophic events using skeletal data from archaeological excavations with special regard to massacres and inter-personal violence. It is well-known, that the age and sex distributions of massacre sites and normal cemeteries formed over an extended period of use show drastic differences (Margerison & Knüsel 2002). Living populations and cemetery populations have different distributions of the average ages of the individuals living in the group/ interred in the cemetery. However, the problems of correctly ageing skeletal human remains and mixed contexts, in which both attritional and catastrophic influences can be found, require an analytical tool which allows researchers to try out and play through different scenarios. The Population & Cemetery Simulator (PCS) allows researchers to model massacres. The Neolithic massacre of Talheim and a possible Late Neolithic war grave in central Iberia are presented as examples.

New radiocarbon dating and demographic insights into San Juan ante Portam Latinam, a possible Late Neolithic war grave in North-Central Iberia.

OBJECTIVES: San Juan ante Portam Latinam is one of a small number of European Neolithic sites meeting many of the archaeological criteria expected for a mass grave, and furthermore presents evidence for violent conflict. This study aims to differentiate between what is potentially a single episode of deposition, versus deposition over some centuries, or, alternatively, that resulting from a combination of catastrophic and attritional mortality. The criteria developed are intended to have wider applicability to other such proposed events. MATERIAL AND METHODS: Ten new AMS 14 C determinations on human bone from the site, together with previously available dates, are analyzed through Bayesian modeling to refine the site's chronology. This is used together with the population's demographic profile as the basis for agent-based demographic modeling. RESULTS: The new radiocarbon results, while improving the site's chronology, fail to resolve the question whether the burial represents a single event, or deposition over decades or centuries-primarily because the dates fall within the late fourth millennium BC plateau in the calibration curve. The demographic modeling indicates that the population's age and sex distribution fits neither a single catastrophic event nor a fully attritional mortality profile, but instead may partake of elements of both. DISCUSSION: It is proposed that San Juan ante Portam Latinam was used as burial place for the mainly adolescent and adult male dead of a particular or multiple violent engagements (e.g., battles), while previously or subsequently seeing use for attritional burial by other members of one or more surrounding communities dead over the course of a few generations. The overall bias towards males, particularly to the extent that many may represent conflict mortality, has implications for the structure of the surviving community, the members of which may have experienced increased vulnerability in the face of neighboring aggressors.

A massacred village community? Agent-based modelling sheds new light on the demography of the Neolithic mass grave of Talheim.

The virtual experiments presented below reveal the counterintuitive archaeological demography of the Neolithic mass grave of Talheim and underline the importance of distinguishing between the demographic structures of living and dead populations, as well as between attritional and catastrophic mortality patterns. We utilise a new agent-based modelling approach called Population & Cemetery Simulator based on the NetLogo programming language and the Behaviour Composer of the modelling4all project, which allows us to extrapolate from dead to living populations and vice versa. Contrary to received opinion, we argue that the population of the Neolithic mass grave holds specific demographic information only, as it represents a pure catastrophic mortality pattern, i.e. a living population at a single point in time rather than the population of a conventional cemetery. The first experiments illustrate why the published demographic data (e.g. mortality, life expectancy, mean age at death) is misleading. It is illogical to utilise mortality tables devised for conventional (attritional) cemeteries in the case of living populations. Modelled populations with the published mortality rates of the massacre site are, furthermore, unable to stand up to plausible human demographic circumstances. In the second part, we evaluate the actual demographic information content of the Talheim sample. Comparative modelling illustrates that the Talheim population appears to be similar to possible living populations based on the mortuary record of Schwetzingen, an isochronal site of the Linear Pottery Culture (LBK), and Bärenthal, a site which dates back to the early medieval period (7th to 10th centuries). It is therefore very likely that the Talheim population is a representative sample of a living population in the LBK and might even represent a massacred village community in its entirety.