Human identification techniques have been a leading tool to hold perpetrators accountable, give families closure, and reconstruct faces on skulls. This project is a pilot study to critically examine three disciplines that fall under the human identification umbrella: forensic anthropology, forensic genetics, and forensic art. Current facial research in genetics focuses on data from living individuals where specific single-nucleotide polymorphisms (SNPs) that influence specific regions of the face have been found. This study assesses the translation of these same regions to craniometric dimensions (inter-landmark distances) of the underlying skull itself. The goal of this project is to provide information regarding the correlation of craniometric measurements and SNPs, as well as encourage interdisciplinary work within the forensic sciences. We examined a selection of candidate SNPs currently identified in the literature to determine if there were correlations between inter-landmark distances and those SNPs within the same individual. A series of 98 craniometric landmarks were collected from 17 documented skulls from the Texas State Donated Skeletal Collection using a 3D Microscribe digitizer. Criteria for inclusion in this study included European American ancestry, the presence of intact skulls, and presence of associated donor blood cards collected at the time of body donation. Using these blood samples, DNA from each individual was extracted, amplified, and sequenced through Next Generation Sequencing for the specific chosen SNPs. Afterward, bioinformatics tests were applied to observe the presence or absence of the major or minor alleles in the specific locations on the genome. After determining the presence or absence of an SNP (minor allele), a set of statistical tests were performed including: Spearman’s correlation between the craniometric measurements and the individual’s genetic data variables; two-way hierarchical clustering and Bootstrap Forest modelling between variables that demonstrated significant correlation; a principal component analysis was performed on the craniometric data (inter-
landmark measurements) and genetic data (SNP presence/absence) in order to check the homogeneity of each data set; and finally, a pair-wise Procrustes analysis was completed on the correlation of the two data sets as different groups. The results indicate a correlation in various degrees between the targeted craniofacial regions and the targeted SNPs. There were 11 SNPs that showed significant correlation (p <0.05). However, the correlations were not as expected and showed some interesting results. By group level there was no significant correlation, however, there was correlation at the individual level. While some SNPs affected the soft tissues only, others showed correlations with the skull (hard tissue), a finding that had not been previously known. By combining craniometric and DNA analyses to leverage genotype-phenotype associations, there is great potential to expand the discourse of current facial approximation and to, thereby, provide new investigative tools for human identification in forensic anthropology.
Afra, Kamar; Algee-Hewitt, Bridget F.B.; and Hamilton, Michelle D., "Understanding the Relationship between Genetic Markers and Skeletal Remains: Implications for Forensic Anthropology and Phenotype-Genotype Studies" (2022). Human Biology Open Access Pre-Prints. 193.