Ancient Celts: A reconsideration of Celtic Identity through dental nonmetric trait analysis.

Abstract The Celts are a collection of tribes and/or populations that inhabited much of Central Europe during the Iron Age and are still something of an enigma. The relationship among the spread of their material culture, the application of Celtic ethnicity, movements among the diverse populations possessing Iron Age Hallstatt and La Tène artefacts throughout Central Europe believed to have been spread by Celtic people, and/or spoken languages identified as Celtic have long been questioned by researchers. However, previous research has primarily focused only on chronological and typological descriptions and documentation of diachronic change. Diverse populations throughout Europe have been intrinsically linked based on perceived similarities in burial practice, art styles and material culture. Subsequently, these associations have resulted in the creation of the so-called La Tène=Celtic paradigm. Under this paradigm, the presence of La Tène artefacts designate a population as Celtic, which is still prevalent in the field of Celtic studies regardless of documented regional differences. The underlying biological diversity among presumed Celtic populations and processes driving the observed variation in artefacts, art styles and burial practices throughout the core and expansion regions (i.e., where the Hallstatt and La Tène material cultures initially developed versus those into which they subsequently spread during the 4th and 3rd centuries BC) are not well understood. The present study helps fill the void in the current understanding of underlying biological diversity among these populations in several ways. First, 36 morphological traits in 586 dentitions from 11 regional samples, from Britain and Europe, were collected using the Arizona State University Dental Anthropological System (ASUDAS). The above samples represent the core and expansion regions, along with a comparative European Iron Age sample outside the known range of Celtic expansion. Frequencies of occurrence for each dental and osseous nonmetric trait were recorded by sample. Second, the suite of traits was compared among samples using principal components analysis, (PCA) and the mean measure of divergence (MMD) distance statistic. Multidimensional scaling was subsequently employed on the symmetric MMD matrix to illustrate graphically inter-sample relationships. Phenetic patterns of overall biological similarity and dissimilarity among individuals and populations based on morphological traits were determined. MMD distances were then compared with geographic distances among samples, under the assumption that genetic affinity is inverse to spatial distance. The biological distance estimates suggest the following. First, populations in the expansion regions exhibit less biological diversity than those within the core. Specifically, two samples within these regions are biologically indistinguishable, the remaining two are biologically distinct, and all samples within the core are phenetically diverse. Thus, populations in the expansion regions are genetically distinct from those in the core and were likely acculturated, not genetically influenced by these groups. Limited intra-and-extra regional gene flow and genetic isolation explain the population structure within the above regions. Second, overall phenetic heterogeneity, biological diversity, and population discontinuity are indicated, as the majority of the samples within both regions are biologically distinct from one another. This diversity may also reflect genetic and linguistic boundaries among the samples. Third, waves of migration from the core during the 4th and 3rd centuries BC were not likely responsible for diachronic changes in material culture within the expansion regions. Fourth, the separation of populations and material culture into the core and expansion regions, and the application of Celtic ethnicity to diverse populations possessing artefacts and a spoken language(s) identified as Celtic may be a nominal association, i.e., in name only. Simply put, the comparative results suggest that these groups represent biologically distinct populations. These findings were compared with published archaeological, linguistic, genetic and bioarchaeological information to test for concordance between dental and other evidence. The present study does not support findings of previous studies and suggests there is more genetic diversity than previously assumed under the La Tène=Celtic paradigm. Thus, a combination of genetic isolation by distance, limited intra-and-extra-regional gene flow, trade, cultural diffusion and/or assimilation is likely responsible for the observed art style, burial practice, archaeological, genetic and linguistic diversity among populations possessing Hallstatt and La Tène artefacts and/or language(s). These diverse populations may have lost their cultural autonomy after being subsumed into a greater Celtic identity. Thus, the contemporary concept of Celts is likely a modern construct that has hindered understanding of the extent of regional diversity and cultural autonomy among diverse populations throughout Iron Age Europe