The opium poppy (*Papaver somniferum*) is a globally significant crop with medicinal, psychoactive, and alimentary uses. Despite its importance, its early history and dispersal have been understudied. This research directly addresses this gap by establishing a chrono-cultural framework for the domestication and spread of the opium poppy in Western Europe. Previous attempts to reconstruct the history of this crop relied heavily on indirect dating methods using associated materials, such as animal bones or charcoal, potentially leading to inaccurate chronological attributions due to issues like post-depositional movement of small seeds. This study overcomes this limitation by utilizing advanced radiocarbon dating techniques to directly analyze minute opium poppy remains (seeds and capsules) from archaeological sites across the Mediterranean and Western Europe. The central research question revolves around determining the precise timing and pathways of opium poppy introduction and spread across diverse regions, allowing for a more detailed understanding of Neolithic agricultural practices and cultural interactions.

Existing research on the opium poppy's origin and spread presented conflicting scenarios. Some hypothesized a Near Eastern origin and subsequent diffusion to Europe alongside other Neolithic crops, while others argued for a European domestication. However, the archaeobotanical evidence supporting a Near Eastern origin is scant, with only a few Pre-Pottery Neolithic sites in the Near East and Anatolia yielding opium poppy seeds, and those findings themselves questioned due to potential intrusion from later layers. The absence of opium poppy remains along the expected dispersal routes from the Near East to Western Europe further weakens this hypothesis. The alternative hypothesis, proposing a Western European domestication of the opium poppy, is more strongly supported by the numerous Early Neolithic sites in Western Europe that have yielded opium poppy seeds, particularly in the Mediterranean region, where the wild relative *P. somniferum* subsp. *setigerum* is still found. However, previous chronological frameworks relied on indirect dating methods, leading to uncertainties about the timing of the crop's appearance and spread.

This study employed direct radiocarbon dating of opium poppy remains from eleven Neolithic sites (5900–3500 cal BCE) across the Mediterranean, Northwestern temperate Europe, and the Western Alps. The selection of sites was based on chronological attribution, location, and the quality of archaeological contextual information. Sites included those attributed to the Impressa, Cardial, Epicardial, Linearbandkeramik (LBK), and Blicquy/Villeneuve-Saint-Germain cultures, representing diverse Neolithic phases and regions. Due to the minuscule size of the opium poppy seeds (microsamples), optimized sampling and preparation protocols were necessary to minimize the uncertainty associated with radiocarbon dating. Where possible, macrobotanical remains (macrosamples) from the same sediment layers were also dated to provide independent chronological control and assess the potential for intrusion of microsamples. The samples were processed using gentle acid washing to preserve the fragile poppy seeds, followed by offline combustion and analysis using a compact Accelerator Mass Spectrometry (AMS) system. Data reduction for macrosamples involved Bayesian Analysis of Time Series (BATS) software, while a constant contamination correction was applied to the microsamples. Calibration of the radiocarbon ages was done using OxCal 4.4 software based on the IntCal20 atmospheric curve. A total of 22 samples were analyzed, including 12 directly dated opium poppy remains.

The radiocarbon dates obtained from the opium poppy remains ranged from 5622 to 4050 cal BCE. The earliest evidence for opium poppy presence was found in La Marmotta, central Italy, dated to 5622-5480 cal BCE. This indicates that the opium poppy was present in the central Mediterranean by the middle of the sixth millennium BCE, possibly growing naturally and being cultivated by early Neolithic communities. The spread of the plant to other regions was relatively rapid: it appeared west of the Rhine by 5300-5200 cal BCE and reached the Western Alps by 5000-4800 cal BCE. Direct dating also revealed instances of intrusion of more recent opium poppy seeds at some sites (Los Castillejos, Těšetice, Buchères, and Smólsk), highlighting the importance of direct dating for accurate chronological reconstruction. The study confirmed the presence of opium poppy in the earliest phases of occupation in several key regions, demonstrating its early adoption into Neolithic farming systems. The results showed a clear chronological sequence, starting in the Mediterranean and moving northwards, with a slight delay in its appearance in the mountainous regions of the Western Alps. This suggests that different environmental factors and rates of Neolithic expansion might have affected the adoption of opium poppy in different areas. The data also suggests a possible link between the introduction of opium poppy to Northwestern temperate Europe and the Mediterranean Cardial culture.

The findings strongly support the hypothesis of a Mediterranean origin for the cultivated opium poppy in Western Europe. The presence of the plant in the central Mediterranean by the middle of the sixth millennium BCE, within its current natural distribution area, makes it plausible that it was initially cultivated from wild populations. The relatively rapid dispersal to northwestern temperate Europe and the Western Alps, despite the different cultural contexts, likely reflects the species' ecological adaptability and its integration into existing agricultural networks. The presence of opium poppy in the early stages of Neolithic settlement in several key regions reinforces its significance as an early addition to the Neolithic crop package. The differences in the timing of its introduction in different regions may be attributed to variations in the rate of Neolithic expansion and environmental factors, indicating a complex interplay between human migration and ecological suitability. The study highlights the importance of direct dating of plant remains, particularly minute samples, for accurate reconstruction of early agricultural practices and dispersals.

This study provides the first comprehensive chrono-geographical framework for the early history of opium poppy in Western Europe, based on direct radiocarbon dating of minute botanical remains. The findings demonstrate a Mediterranean origin and subsequent relatively rapid dispersal across various regions, highlighting the species’ ecological adaptability and its incorporation into early Neolithic economies. Future research should focus on further refining the chronological framework with additional sites, exploring the details of domestication processes using geometric morphometrics, and investigating the broader impact of opium poppy on Neolithic societies and their interactions.

The study acknowledges the inherent limitations of working with small, fragile plant remains. The small sample sizes and the associated uncertainties in radiocarbon dating may have affected the precision of the obtained chronological framework. The possibility of post-depositional disturbance, even with the careful selection of samples, also needs to be considered. While efforts were made to minimize these issues, the presence of modern intrusions in some samples underlines the continued importance of applying advanced dating techniques and meticulous site analysis. Finally, the study primarily focuses on the appearance and spread of the opium poppy; a detailed investigation into its uses within Neolithic society requires further research.