Pigs on carts?
Chemical signals locked into tooth enamel reveal more about the exchange of goods (and animals) over 4,000 years ago
Movement of resources was essential to the survival and success of early complex societies. The sources and destinations of goods and the means of transportation – be it by boats, carts and/or foot – can often be inferred, but the logistics of these movements are often more difficult to ascertain.
In a new study, published today in Scientific Reports, researchers used strontium isotopic analysis to test hypotheses about the role of animal and animal-powered transport in medium and long-distance movement and exchange, using the Indus Civilization as a case study.
Across the wide geographical spread of the Indus Civilisation, there is strong evidence for long-distance exchange of raw materials and finished objects and this process is presumed to involve boats and animal-driven transport, although there is little evidence as to the relative importance of each mode of movement.
Archaeologists analysed 94 samples of tooth enamel from 39 animals. From cattle, to water buffalo, goats to pigs, a variety of animals were included in the study.
Strontium isotopic analysis of animal remains from four sites analysed for this study combined with results from nine other sites indicates limited long-distance animal movement between different geological zones within the Indus Civilisation.
These findings suggest that individual animals primarily moved short- or medium-distances, though there are several significant exceptions seen in some pigs and cattle found at two large urban sites.
Strontium isotopic analysis is a technique used to unlock chemical signals trapped in tooth enamel. Strontium levels in tooth enamel reflects the geology of the area in which that individual lived, and ate.
The strontium levels in an area are dependent on many factors, including the geology of the area, the composition of the soil and river deposits. Soil samples from areas throughout the Indus River Basin were analysed to create ‘Isozones’ of the Indus Valley Civilization.
Due to tooth formation, and animal lifetimes, it is possible to trace animal origins based on their strontium content. It is then possible to determine whether these animals moved small, or larger, distances during their lifetime.
The authors have inferred that long-distance transport of goods, be it raw materials, finished objects, other goods, or the animals themselves, likely involved the use of boats and waterways, where they were present.
In the extensive areas where there was no water, or when waterways were difficult to navigate at certain times of year, there was likely widespread use of traction animals moving over short, medium and occasionally longer distances.
The data gives some support to the suggestion that different animals participated in many short to medium-distance movements, but also confirms that some animals moved or were moved hundreds of kilometres.
Surprisingly, the only animal that travelled ‘long’ distances, were pigs. Cattle and other bovids only being used to travel short distances.
Several theories have been put forward as to why this may have been the case; perhaps teams of cattle were swapped after short distances, in a formal system of the exchange of goods. Perhaps, it was much more informal, the evidence is unclear. This research is supported by evidence to show similar transportation of pigs in Neolithic Britain and Bronze Age Greece.
"There is clearly considerable scope for future research into and theorising about the systems of exchange and movement in the Indus River Basin. Amongst a range of possible approaches, the Indus case is ideal for exploration through network and agent based modelling that consider the distribution of individual products, their quantities and the ways in which these patterns change over time."
Cameron Petrie is the lead author on the paper.
His research primarily focuses on the investigation of complex societies - particularly interested the rise of complexity, state formation, the impact imperial expansion, and the relationships between humans and the environment. He has extensive field and research experience at archaeological sites dating from the Neolithic up to the medieval period in India, Pakistan and Iran, and has co-directed projects in each of these countries.
Dr Tamsin O'Connell is a main contributor to the paper.
She is a chemist focussing on biomolecular archaeology and isotopic analysis in archaeological and ecological contexts. Her research traces signals of diet and climate in human and animal tissues, using isotopic analysis.
She is Head of the Department of Archaeology at the University of Cambridge and a Reader in Isotopic Ecology.
The paper is published in Scientific Reports here.
The TwoRains project had a formal collaboration with Banaras Hindu University – Prof. Ravindra Nath Singh
Co-authors include collaborators from Deccan College Pune (Prof. Vasant Shinde and Prof. Pramod Joglekar).
To find out more about the project, you can access the TwoRains project page here.
The research was funded by a ERC Consolidator grant - Horizon 2020 research and innovation programme and the UKRI Global Challenges Research Fund.
Published 2 January 2024
All images: Cameron Petrie
The text in this work is licensed under a Creative Commons Attribution 4.0 International License
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