Stable C and N isotope analysis of human dental remains retrieved from an ancient well at Ajnala (Punjab, India): Assessment of Dietary status and geographic affiliations

Abstract

Stable isotope analysis of biogenic tissues like tooth and bone has become a widely recognized and increasingly important method for provenance of human remains, particularly in bio-archaeological and forensic investigations. Establishing the dietary status and identity of unknown human skeletal remains retrieved from forensic anthropological contexts is a challenging task. Thousands of unknown human osseous remains along with the personalized contextual items, reportedly belonging to 282 Indian soldiers killed in 1857, were excavated non-scientifically from an abandoned well at Ajnala (Amritsar, India). In present study, the isotopic concentrations of carbon (C) and nitrogen (N) were estimated from the dentine collagen extracted from 21 first molars to provide information about the geographic affinity and dietary status of the individuals killed in Ajnala. As diagenesis affects bone more severely than enamel or dentine due to increased porosity of the former, so teeth were preferred to bones for stable isotope analysis in present study. The literature supported C: N range of 2.8-3.6 was considered as cut-off for the well-preserved collagen and the samples with values outside this range were considered to be altered or contaminated with non-collagenous materials. The interpretation of the obtained isotope values from Ajnala teeth samples indicated the consumption of C3/C4 mixed diet (though some samples showing marine diet) by the victims which supported the previous observations about the dietary status of Ajnala victims estimated from prevalence of various dental pathologies. Though C and N isotopes are generally not the best indicators of geographic origin, they can be used to for the purpose only if they show different dietary inputs of C3 and C4 plants. Present study results provided scientific confirmation to the written historical accounts that Ajnala skeletal remains belonged to the individuals belonging to the Indian states of Awadh (north-eastern Uttar Pradesh), Bihar and Bengal and some norteastern states.