The burial in question belongs to the Qin state, the polity that would eventually unify China in 221 BCE after centuries of warfare during the Warring States era (roughly 475 to 221 BCE). Qin cemeteries from this period have yielded rich evidence of social stratification, ritual practice, and craft production, but intraoral objects remain rare and poorly understood. When excavators encountered the stone within the dental arcade of the buried individual, its position raised an immediate question that could not be answered by visual inspection alone: had the stone been placed deliberately at the time of burial, or had it entered the oral cavity after death through natural processes such as soil intrusion?

Answering that question required what the researchers describe as a differential bioarchaeological assessment, meaning that multiple competing hypotheses were formulated in advance and tested against independent lines of physical evidence. The first hypothesis held that the stone was a deliberate funerary deposit, inserted into the mouth as part of a mortuary ritual. The second proposed accidental incorporation, in which sediment movement or decomposition of soft tissues allowed a stone from the surrounding fill to migrate into the oral space. A third possibility considered was that the object had a physiological origin, for example as a bezoar or concretion formed within the body itself. Each scenario carries distinct implications for taphonomy, for ritual interpretation, and for the study of ancient beliefs about death and the body.

To discriminate among these scenarios, the team combined macroscopic and microscopic examination of the stone with detailed documentation of its position relative to the teeth, mandible, and cervical vertebrae. The stone’s surfaces were inspected for use-wear, modification traces, and adhering materials. Microscopic analysis sought evidence of deliberate shaping, such as grinding facets, polished planes, or flaking scars that would indicate human manufacture rather than natural stream or soil abrasion. The sediment trapped in the surrounding context, including material between the teeth and within the oral cavity, was compared with the grave fill above and around the burial to determine whether the matrix associated with the stone matched the original depositional environment or showed signs of later intrusion.

The materials characterization extended to mineralogical identification, because the type of stone itself is informative. Techniques such as petrographic assessment, scanning electron microscopy with energy-dispersive X-ray spectroscopy, and Raman or similar spectroscopic methods allowed the researchers to determine the rock’s composition and texture. Comparing that signature with known geological sources in the region provided a preliminary indication of whether the stone was locally available or had been transported. Trace residues on the surface, including possible organic films, mineral encrustations, or precipitates consistent with prolonged contact with dental enamel and bone, were mapped and chemically characterized. Such residues are central to the differential assessment, because prolonged intimate contact with oral tissues should leave a distinctive pattern of surface alteration that a stone accidentally swept into a grave void would lack.

The position of the object within the dental arcade proved especially significant. A stone deposited during burial rites would plausibly rest in a stable, constrained position, often wedged between the mandibular or maxillary teeth, with its long axis conforming to the space available. A stone that migrated after burial would more likely rest beneath the collapsed mandible or on the floor of the burial pit in an unconstrained orientation. The excavation documentation, including photographs, three-dimensional recording of the find spot, and stratigraphic drawings, allowed the team to evaluate the object’s orientation and support. Combined with the sediment-matrix comparison and the surface-alteration evidence, the integrated data favored an interpretation of deliberate placement rather than passive intrusion, though the authors are careful to present their conclusions as probabilistic rather than absolute, in keeping with the logic of a differential assessment.

Beyond the mechanics of deposition, the study situates the find within a broader anthropology of mouth deposits. In Chinese funerary tradition, objects placed in the mouth of the dead, sometimes called han in later textual sources, range from jade cicadas in Han dynasty burials to coins, shells, and pearls in other periods and regions. These deposits are commonly interpreted as provisions for the afterlife, symbols of rebirth, or attempts to seal the body against decay and malevolent influence. Jade is the material most often discussed in the textual and archaeological record, which makes a plain stone object from a Qin burial particularly interesting. If the identification of deliberate placement holds, the find suggests that the practice of intraoral deposit was not restricted to elite jade artifacts but extended to humble, locally sourced materials, potentially broadening the social range of the rite.

The bioarchaeological component of the assessment also involved the human remains themselves. The researchers evaluated the dentition for pathology, wear, and post-mortem damage, since the condition of the teeth constrains both the timing of insertion and the physical possibility of placing an object of a given size into the oral cavity. Evidence of periodontal disease, caries, or ante-mortem tooth loss can indicate whether the individual was edentulous at death, which would affect the stability of an inserted object. The age and sex estimation of the individual, together with any observable indicators of health status, provides social context: intraoral deposits may have differed by age, gender, or status within the Qin community, and each well-documented case contributes to building that comparative framework.

Methodologically, the article is a case study in how heritage science can resolve questions that older excavation reports left open. Many intraoral objects discovered in earlier decades were recorded only in photographs or brief notes, and their mode of deposition was asserted rather than demonstrated. The differential approach modeled here, in which hypotheses are specified, tested with independent techniques, and compared for explanatory power, offers a template that can be applied retrospectively to museum specimens and prospectively to future excavations. The authors emphasize that no single technique is decisive: mineralogy, micromorphology, residue chemistry, spatial documentation, and osteology must converge before a deliberate funerary deposit can be argued with confidence.

The find also carries implications for the archaeology of the Qin state specifically. Warring States Qin mortuary practice has often been characterized through large cemeteries, stamped-earth tombs, and later imperial monuments, while small-scale ritual behaviors of ordinary burials are less visible. A carefully analyzed intraoral stone adds texture to this picture, indicating that communities on the Qin periphery participated in symbolic practices concerning the mouth and the passage of the dead, even when exotic materials were unavailable or not socially appropriate. As the dataset of differentially assessed cases grows, it may become possible to trace the geographic spread, chronological development, and eventual textual codification of the mouth-deposit rite, linking the silent stones of excavated graves to the rich corpus of Chinese ritual writing that began to describe such customs in later centuries.

Subject of Research: Bioarchaeological analysis of a stone object deposited inside the mouth of a Warring States-period Qin burial in China

Article Title: Differential bioarchaeological assessment of an intraoral stone object from a Warring States-period Qin burial, China

Article References: Wang, S., Zhang, X., Wang, C., & Zhou, Y. (2026). Differential bioarchaeological assessment of an intraoral stone object from a Warring States-period Qin burial, China. npj Heritage Science. https://doi.org/10.1038/s40494-026-02987-6

Image Credits: AI Generated

DOI: 10.1038/s40494-026-02987-6

Keywords: bioarchaeology, Warring States period, Qin burial, intraoral deposit, funerary ritual, heritage science, taphonomy, ancient China, mortuary practice, dental anthropology, archaeological science, stone artifact