Abstract
ObjectivesThe anatomical features of the atlanto‐occipital joint can be potentially useful in re‐associating or excluding crania to atlases in commingled remains. This study investigated whether linear measurements and the 3‐dimensional (3D) surface of occipital condyles and articular facets of atlases can represent valid insights for this purpose.MethodsThe variations among eight corresponding linear distances were analyzed in a sample of 150 individuals through six supervised machine learning techniques attempting to develop classifiers able to identify elements belonging to the same individual. Furthermore, a 3D analysis was conducted on the articular surfaces through superimpositions of 3D models of corresponding and non‐corresponding crania and atlases obtained by using respectively stereophotogrammetry and laser scanning. This analysis investigated differences in terms of point‐to‐point distances (Root Mean Square, RMS) of superimposed 3D surfaces.ResultsNone of the six machine learning techniques were able to correctly detect a satisfying percentage of correspondent pairs in the overall sample by using the linear variables. The 3D analysis of the articular surfaces found RMS values over 0.53 mm only for superimposed non‐corresponding surfaces, which sets a threshold value to identify 32% of incorrect pairs.DiscussionThe re‐association of cranium to atlas proved to be challenging and hardly possible when considering only metric variables. However, the 3D geometry of the articular surfaces represents a valid variable for this purpose and 3D analyses pave the way for an initial exclusion of incorrect re‐associations, thus should not be considered as a re‐association method per se, but as an exclusionary screening technique.
Highlights
Commingled human remains refers to the mixing of skeletal remains of two or more individuals, regardless of cause or context
Our study revealed the 3D analysis did not allow for the development of a re-association method for crania and atlases, as the original intent of the direct osteometric approach, but it provides at least additional information that can be useful for an exclusionary screening process
It is widely accepted how challenging can be to find a perfect congruence in linear and 3D geometry between the articular surface of two articulating bones and in particular between the atlanto-occipital joint: the ‘in vivo’ anatomy of such structures surely is not perfectly reflected in dry bones, where many of the structures participating in the overall ‘in vivo’ articulation are missing
Summary
Commingled human remains refers to the mixing of skeletal remains of two or more individuals, regardless of cause or context. The commingling can be limited to few subjects, as in the case of graves of multiple individuals or in fatal motor vehicle accidents, or it can be extended to a large number of individuals, as in cases of mass graves or mass disasters Whether such contexts pertain to archeological or forensic scenarios or comprise a few or hundreds of individuals, the aim of anthropologists is the re-association of the entire skeleton of each individual in order to reconstruct their story and identity. Osteometric techniques measure bone sizes and create regression models based on linear relationships between bones in order to compare their similarity with the final purpose to characterize referenced normal size and relationships among bone elements (Byrd, 2014) This is accomplished using estimates of population parameters (mean and standard deviation (SD)) from reference data, used to formulate the statistical hypothesis to be subjected to a significance test (Byrd, 2014; Fisher, 1958)
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