Across Eurasia, the use of copper and its alloys became widespread from 3000-1000 BCE. A comprehensive new database is helping scientists understand the chemistry of the Bronze Age and the spread of the technology. Along with innovative mapping and visualisation tools, this database is providing a timeline of human interaction. Objects come and go but the metals from which they are made can last much longer as they are melted down and re-used, according to FLAME project coordinator Mark Pollard, professor of Archaeological Science at the Research Lab for Archaeology and the History of Art, University of Oxford. “We have a new approach which considers the life cycle of the underlying ‘flow’ of material rather than biographies of individual objects,” he explains. The FLAME project, supported by the European Research Council, links social, scientific, chronological and geographical aspects of early metallurgy. “We use the patterns within the chemical and lead isotopic compositions of the metal objects to understand these interactions and how this technological innovation of the time spread,” he says. “In the Bronze Age, Eurasia was a connected entity with a series of civilisations and societies which were in contact with each other, like a chain,” adds Pollard, noting the prevalence at the time of nomadic communities, particularly in huge parts of Central Asia and Siberia.
Reinterpreting lead isotope data
Conventionally, lead isotope data was used to determine the age of the ore deposits. But the project devised new tools to interpret chemical and isotopic data from metals to produce a timeline of human interaction during the life of a metal object from ore extraction to final resting place in archaeological sites. The scale and scope of the project – unparalleled globally in terms of Bronze Age metallurgy – enabled a radical reinterpretation of lead isotope data. In particular, that small shifts in chemistry do not necessarily mean a different ore source but could be the consequence of human interaction with metals, including processing, mixing or recycling metals. During most of the period, copper was hardened with arsenic or tin. “We looked for trace elements – arsenic, antimony, nickel and silver – in the metal. They behave differently on models of recycling and circulation. We developed a robust methodology to produce maps of Eurasia showing the distribution of various combinations of these trace elements in metals. They are related to a source, but they are also related to patterns of trade and exchange,” Pollard explains.
Bringing ‘legacy’ and latest data together for a more accurate picture
The project’s initial aim was to build a geographic information system (GIS) database combining research published in the past 70 years with newer scientific research. “With a map you can begin to look at distribution patterns and location patterns. This helps researchers to ask pertinent questions, whether the focus is intercontinental, regional, individual sites or individual graves,” Pollard notes. GIS also allows geospatial analysis such as evaluating the importance of rivers or mountain passes in the movement of metal, he says. But combining older, ‘legacy’ data with newer scientific analysis using sophisticated instruments was a challenge, so robust new methods for characterising metal had to be devised to take this into account. “A lot of ‘legacy’ work was done in the 1960s using techniques which are no longer used. There’s something like 100 000 chemical analyses over this area and this period that we can’t replicate,” he adds. The database will be open access and will include some 120 000 chemically analysed objects.
FLAME, archaeology, Bronze Age, metals, metallurgy, isotopes, Isotopic data, bronze, tin, arsenic, nickel, silver, antimony, copper, GIS, geographic, Eurasia