Biological distance analysis (also known as biodistance analysis) is a methodological approach used primarily in biological anthropology, bioarchaeology, and forensic anthropology to infer genetic similarity or difference among deceased humans based on skeletal traits. It is commonly used when ancient DNA (aDNA) is poorly preserved or when destructive sampling is not feasible for ethical or curatorial reasons. Biodistance studies contribute to our understanding of phylogeny, migration, kinship, and ancestry.
The study of skeletal morphological variation to identify group relationships has a long history, dating back to the 18th century. Early work focused primarily on categorizing global human variation based on cranial anatomy using racial typology. In the 1970s, influenced by the New Archaeology movement, biodistance studies were repurposed to focus on reconstructing population structure and history within archaeological contexts. Modern biodistance research rejects typological thinking in favor of emphasizing within-population variability. Recent methodological advances in computing, statistics, and 3D scanning have further refined these analyses by enabling more accurate assessments of multivariate variation within a population and quantitative genetics framework. In the 21st century, the field has increasingly integrated genetic data, including mitochondrial DNA, Y-chromosome markers, and autosomal DNA sequences, to complement traditional morphological approaches.
The method is closely related to archaeogenetics but differs in that it uses skeletal morphological features rather than molecular data. Cranial and dental traits are typically favored because they are highly heritable and shaped primarily by neutral evolution. The four most widely used data types are craniometrics, odontometrics, cranial nonmetric traits, and dental nonmetric traits collected via the Arizona State University Dental Anthropology System (ASUDAS). The rationale for using these traits as proxies for genetic relatedness stems from heritability studies. A study published in 2023 found that ASUDAS dental nonmetric traits are among the most informative morphological markers for biodistance analysis, significantly outperforming other commonly used data types.
Biodistance analyses have been used to assess genetic relationships both between individuals and among populations, with applications ranging from local studies within archaeological sites to broad comparisons across continents. The degree of similarity or dissimilarity is typically quantified using mathematical distance functions, such as the Mahalanobis distance, Smith's Mean Measure of Divergence, and the Gower distance. For visualization, biodistance studies often employ ordination techniques, such as multidimensional scaling (MDS), as well as hierarchical clustering methods like the unweighted pair group method with arithmetic mean (UPGMA).
In bioarchaeology, biological distance analysis is used to study kinship, migration, post-marital residence patterns, and population structure in ancient societies. Some examples are listed below:
In forensic contexts, biodistance analysis can support the identification of unknown individuals by estimating ancestry and assessing familial relationships. Some examples are listed below:
In paleoanthropology, biodistance data can help elucidate hominin phylogeny, population dispersals, and past admixture events. Some examples are listed below: