Multiregional Pb isotopic linear patterns and diagenesis: Isotopes from ancient animal enamel show Native American foreign war trophies are local ancestors

Skull burials are found all over the world and often are interpreted to be foreigners, sacrifices, or victims of warfare. The cause of ancient Native American skull deposits often leads to disagreement among scholars torn between warfare and ancestor veneration. Most previous research suggested a Caddo skull-and-mandible deposit (consisting of clusters of skulls and clusters of isolated mandibles) in southwest Arkansas, USA contained foreign victims of interregional warfare, representing at least 352 people (1253-1399 CE). While Sr isotopes are commonly used in archaeology to investigate such issues, they did not provide a conclusive answer to the geographic origin of the remains. This study advances the biologically available Pb method by constructing a large-scale multiregional Pb isotopic background with ancient animal tooth enamel and uses their associated linear patterns to evaluate human geographic origins. Evaluation of Pb contamination through diagenesis in human tooth enamel is evaluated and advanced using correlation analysis of trace elemental data from teeth and burial soil. A total of 180 animal teeth were processed from 28 ancient sites in the southcentral USA. Combining Pb isotopic linear patterning analysis with the Sr isoscape allows us to establish that the skulls and mandibles are local to southwest Arkansas and indicate or strongly suggest they are non-local to all other tested regions. This illustrates the importance of Pb isotopes in studies of human geographic origins. It also provides one cautionary tale that interpretations about violence related to detached skulls should be evaluated with appropriate methods and evidence and with a critical eye for other explanations. This study was conducted in collaboration with the Caddo Nation of Oklahoma and provided both the descendant community and researchers with answers to the questions surrounding the remains, serving as one example of how stakeholders can come together and produce positive outcomes.

Automated summary

Skull burials around the world have been interpreted as foreigners, sacrifices, or victims of warfare. The cause of ancient Native American skull deposits, specifically in southwest Arkansas, has sparked debate among scholars. This study used a new method, the biologically available Pb method, to determine the geographic origins of the remains and concluded that the skulls and mandibles were local to southwest Arkansas.