This research highlights a reorganization of metal production and circulation, with initial centers in the Eastern Mediterranean, followed by a shift in gravity towards Western and Central Europe during the transition between the Bronze and Iron Ages. The findings were published in Science Advances.
The quest for metals has played a major role in the history of societies. Galena, a lead sulfide often rich in silver, was used to produce coins, objects, and urban infrastructure. Its extraction released lead into the atmosphere, preserved in natural archives like peat bogs. These archives have allowed the reconstruction of past atmospheric lead fallout, but identifying the originating mining regions remained challenging.
To overcome these difficulties, a new method, EMII ('Environmental Match Intensity Index'), was developed. It analyzes lead isotopic signatures in environmental archives and compares them to a database of ores. The study incorporates data from a peat bog core in the Pilat massif, covering six millennia.
The results reveal a transformation in metallurgical organization. In the Late Neolithic and Chalcolithic periods, the first detected correspondences in peat bogs are concentrated around the Laurion mining region in Greece. During the Bronze Age, the system extended to the Eastern Mediterranean via maritime trade networks. The transition to the Iron Age marked a major change with a westward shift of the center of gravity, involving Western and Central Europe (Massif Central, Rhine and German massifs, British mining areas) connected by multimodal networks.
This finding challenges the traditional model that places the Iberian Peninsula at the center of lead and silver supply from the Iron Age onwards. EMII highlights the long-underestimated role of several continental and British mining regions. The highest EMII level is reached during the High Roman Empire, which adopted and intensified the polycentric and multimodal organization already in place during the Iron Age.
In the contemporary period, the decrease in EMII does not mean lead pollution is diminishing but rather reflects a modification of its origins, now stemming from increasingly diverse and globalized industrial sources. This research demonstrates that peat bogs can illuminate not only the history of pollution but also that of ancient economies and exchange networks, showing a shift from a primarily maritime Eastern metallurgical system to a Western, polycentric, and multimodal organization.
