MADURAI: In a significant development, pottery fragments taken from two major archaeological sites, Keeladi in TN and Gottiprolu in Andhra Pradesh, have yielded chemical evidence suggesting the consumption of cow’s milk and plant foods such as peanuts in South India between 600 BCE and 100 BCE.
According to researchers, the specific “biomarkers” that indicate the presence of cow’s milk have not been previously reported in south India.
“All previously reported biomolecular data are geographically restricted to Northern India and are primarily associated with the Indus Valley Civilisation. To our knowledge, the present study provides the first direct chemical evidence that we have successfully extracted in prehistoric South India,” the authors highlighted.
The study was published in npj Heritage Science, a Nature Portfolio journal, on October 29. Authored by seven researchers, it is the outcome of at least four years of work.
Cow milk biomarkers found in archaeological lipid extracts in Keeladi and AP samples
Explaining the process to TNIE, corresponding author Dr C Vijayanand and the study’s first author, Prakash VS, a Senior Research Fellow (CSIR) at VIT, said food molecules released during cooking can become trapped in the microscopic pores of unglazed clay pots. The molecules bind tightly to the clay, which helps protect them from groundwater and microbial decay, allowing some to survive intact for thousands of years. These preserved molecules serve as “biomarkers”, or chemical fingerprints that reveal the possible plant or animal origins of ancient meals and help researchers map early diets and trade routes.
K Rajan, adviser to the State Archaeology Department, told TNIE that technological advances were helping researchers determine what archaeological pots once contained. He cited the study as an example of how newer analytical methods were revealing their contents.
Vijayanand, associate professor at VIT, Vellore, stated that Organic Residue Analysis (ORA) is a vital technique in archaeology, providing molecular insights into the dietary habits, culinary traditions, and trade networks of ancient societies. However, conventional gas chromatography-mass spectrometry (GC-MS) often fails to detect complex, high-molecular-weight dietary biomarkers.
The team, therefore, used a liquid chromatography-mass spectrometry method, UPLC-Q-ToF-MS/MS, to analyse residues in four unglazed pottery sherds: two from Keeladi, dated to the sixth to second centuries BCE, and two from Gottiprolu, dated to the second to first centuries BCE. Non-destructive X-ray micro-computed tomography was used to examine the pottery’s internal structure.
The researchers identified a specific complex organic molecule (a linear A-type procyanidin tetramer) that strongly pointed to the consumption of peanuts or similar nuts. To confirm this, they analysed modern-day peanuts. Peanuts are rich sources of a linear A-type procyanidin tetramer.
While peanut skins make up less than 3% of a peanut’s weight, they contain about 17% procyanidins, mostly oligomers with a degree of polymerization of 2 to 4. “The molecular ion peak, the fragments, and the fragmentation pattern of the procyanidin extracted from the modern-day peanut skin exactly match the mass spectra of the procyanidins extracted from the pottery,” the researchers stated.
Additionally, the team identified six distinct cow’s milk biomarkers in the archaeological lipid extracts. At both archaeological sites, zooarchaeological assemblages are dominated by Bos indicus faunal remains.
Therefore, the observed organic residues from cow’s milk may be from Bos indicus. This suggests that the societies primarily depended on agriculture, cattle rearing, and dairying practices.
The paper nevertheless cautions that the findings from four sherds demonstrate the potential of the analytical method and should not be treated as representative of the wider population’s diet. Its identification of the food sources rests on chemical comparisons rather than definitive biological identification.
The article is titled “Biomolecular evidence of early dairying and plant processing in 600 BCE–100 BCE South India”.
Alongside Vijayanand and Prakash, the research team includes A Thennarasan (VIT), K Manivannan (Archaeological Survey of India), Deepa Sathish (PSGR Krishnammal College for Women), T Sreelakshmi (ASI), and R Sivanantham (State Archaeology Department).
