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FLow of Ancient Metals across Eurasia (FLAME): New frameworks for interpreting human interaction in Later Prehistory

Periodic Reporting for period 3 - FLAME (FLow of Ancient Metals across Eurasia (FLAME): New frameworks for interpreting human interaction in Later Prehistory)

Reporting period: 2018-10-01 to 2020-03-31

The issue being addressed is the interrelationships between the many cultures across Eurasia during the Bronze Age, focusing primarily on the period c. 3000 - 1000 BCE. This is the time when the use of copper alloys spread from the area of the origin of copper smelting and alloying (somewhere around Anatolia and the Balkans), at around c. 5000 BCE or perhaps earlier, arriving on the border of China some time around 2000 BCE. What is the nature of the series of interactions that gave rise to this technological spread? We are using patterns within the chemical and lead isotopic compositions of the metal objects themselves to understand these interactions. The overall objective is to contribute to our understanding of the nature the complex interactions across Eurasia in the Bronze Age. This is important historically, but also helps us to understand the origins of modern Eurasia. In particular, we think that it will change our perception of the role of the mobile pastoralist people of the Steppe. Conventionally, they have simply been considered as the conduit through which the 'civilized' societies of Europe and China have interacted, but it seem s likely that they have been much more active participants in the history of Eurasia.
Much of the first part of the project has been involved in developing a suitable database to host the large quantity of analytical data created over the last 200 years. This has involved considerable work in evaluating the quality of the analytical data - particularly that created by now-obsolete methods - and also ensuring that the archaeological data are as consistent as possible across Eurasia. There are obviously considerable differences in typological descriptions across the major archaeological traditions of Eurasia, as well as considerable variations in chronological descriptions. This database is interfaced to a Geographical Information System (GIS), which allows mapping, but also geospatial analysis such as evaluating the importance of rivers or mountain passes in the movement of metal.

We have also put considerable effort into developing a new theoretical framework within which to analyses these data. This has become known as 'Form and Flow', and is a dynamic model which focuses not on individual objects but on assemblages of objects, and essentially considers the underlying stock of metal rather than specific objects. These assemblages are created according to the nature of the question - an assemblage could be all the objects in a tomb, or all the objects from a particular archaeological horizon at a specific site, or all the objects of a particular type across Eurasia. The key element of this theory is first to look at change in the archaeometallurgical record - change over time, as one culture succeeds another, or change across space by comparing several contemporary sites. This model leads to a new set of tools with which to interpret these data. These include an approach known as 'Copper Groups', which uses data on the commonly measured trace elements (arsenic, antimony, silver and nickel) to look at the common patterns of trace elements in the data. A similar approach is taken to re-defining the categorization of the types of alloys used in antiquity, as opposed to using modern engineering definitions. This approach offers the possibility of defining 'primary' and 'secondary' alloying practices, the latter which might represent substantial metal recycling. It also leads to speculation about the existence of 'Regional Alloying Practice', which is a way of going from the chemical composition of objects to the minds of the foundry metalworkers who were creating these alloys.

Perhaps the most radical work has been to re-think the interpretation of lead isotope data in archaeological metals. This is based on plotting 1/Pb (the inverse of the lead concentration in each object) against one of the lead isotope ratios measured in the same object (we use 206Pb/204Pb). This has the advantage of combing chemical and isotopic data in the same diagram, but also allows mixing lines to be highlighted - mixing of different sources of lead, or mixing of copper with lead. We suggest that this method is more appropriate to interpreting lead isotope measurements from archeological artefacts than the conventional approach of plotting pairs of lead isotope ratios.

In terms of archaeological studies, we have spent considerable time looking at the circulation of metal within Bronze Age China, and also the interaction of the metalworking traditions of the Steppe and Central China. This latter issue is particularly important in understanding the origins of the Chinese Bronze Age, since it is widely accepted that metalworking arrived in China from the Steppe to the west and the north. This work has included a study of the metalwork from southern Siberia, particularly the Minusinsk basin and Mongolia. Another particular focus in China has been the long-standing question of the origin of the highly radiogenic lead used during the Shang dynasty (c. 1600 - 1043 BCE). The actual sources of the lead are still to be identified, but our work has shown that there are likely to have been more than one source of highly radiogenic lead used, and that these could be widely distributed across China.

In western Asia, we have focussed originally on Iran, but have recently expanded this to include Anatolia, the Caucasus, the Levant, Mesopotamia and the Gulf. One of the key issues here is the origin and spread of alloying copper with tin to produce bronze. This is likely to have started almost as soon as the smelting of copper (at least 5000 BCE), but there was a major change during the third millennium BCE, both in terms of the metal sources used and the alloying technology, which gave rise to a rapid increase in the ubiquity of bronze. Attention in Europe has concentrated on the Iberian peninsula, as well as the Atlantic coastal trade.
We would argue that the theoretical and methodological approach delivered by this project offers a radical new framework within which to interpret chemical data on archaeological copper alloys. This starts with the view that, rather than ignoring the many thousand of analyses that have been collected over the last 200 years, it is more productive to develop a series of methodologies which can accommodate these data. This is because of the cost of collecting such a large body of new data, but also because of the virtual impossibility of re-sampling these objects. We then focus on determining change in the chemical and isotopic data, either over time or space, or both, rather than assuming that the key question is provenance. Such change could be due to changes in the source of the metal, but could also be a result of continuing human interaction with the flow of metal.

We expect to expand the data in the current database, perhaps up to more than 120,000 chemically analyzed objects, and perhaps 10,000 lead isotope measurements. This database will be openly publically available at the end of the project. In trms of regional studies, we expect to focus more on western Asia and Europe than the first half of the project.