Not So Linear After All: Reassessing the Chronology of the Transition from Earliest LBK to Flomborn

Abstract The Ammer Valley (SW-Germany), a 23 km tributary of the Neckar River, holds the southwesternmost known sites of the earliest Linear Pottery Culture (LBK). A targeted radiocarbon dating strategy based exclusively on short-lived samples and excluding charcoal entirely, combined with Bayesian modelling, places the earliest settlement activity at around 5330 calBC. Similar results have recently been obtained at numerous other sites using comparable methodologies, suggesting that this date represents a broadly consistent beginning of the LBK across much of its distribution area. Dating the transition from the earliest LBK to the subsequent Flomborn phase, however, remains more problematic. OxCal models indicate that the apparent chronological separation between these phases is driven less by the radiocarbon measurements themselves than by the shape of the calibration curve and may therefore partly reflect a modelling artefact. The posterior probability distributions of both phases overlap substantially within the same calendar range. Consequently, the absolute chronology of the earliest LBK may end too early, while that of the Flomborn phase may begin too soon. Accounting for this effect provides a more convincing explanation for the persistence of unchanged earliest LBK assemblages alongside early Flomborn elements. To address this issue, a second model using trapezium priors was developed alongside the conventional model based on uniform boundary priors widely employed in LBK chronology. Because trapezium priors are specifically designed to model overlapping phases, they reduce the bias described above. The analysis also integrated GIS-based approaches with stylistic criteria derived from ceramic decoration, since typological approaches based on linear developmental trajectories reach their interpretative limits during the transition from the earliest LBK to the Flomborn phase. This combined approach enables a more nuanced reconstruction of LBK expansion within the Ammer Valley and offers new insights into possible interactions with the local Late Mesolithic population.