Ancient DNA investigations at Samtavro, Republic of Georgia

© 2016 Luka PapacThe Samtavro cemetery, used from the Late Bronze Age through to the Early Middle Ages, is the largest known ancient burial ground in the Republic of Georgia and the Caucasus. Centrally located at the crossroads of major continents and trading networks, archaeological investigations have revealed a diverse assemblage of artefacts and cultural practices, including Greek, Roman, Persian, and Hunnic influences. In order to gain insight into the origin, affinity and legacy of the Late Antique (~300-500AD) Samtavro population, we sequenced whole mitochondrial genomes (mitogenomes) from 17 individuals buried in 14 tombs. In order to test whether tombs were being used to bury family members together, we sampled more than one individual from three different tombs. We find high mitochondrial DNA (mtDNA) diversity with all individuals from different tombs (n=14) carrying unique mtDNA haplotypes. Identical mtDNA haplotypes were found in two of the three tombs from which two individuals were sampled, probably reflecting the co-burial of kin. Fifteen individuals were included in a principal components analysis (PCA) of haplogroup composition and fourteen individuals in a multidimensional scaling plot (MDS) of Slatkin’s Fst values. These analyses show a strong west Eurasian influence with close affinity to populations from the Caucasus, Middle East and Europe. All (n=17) mitochondrial lineages belong to West Eurasian haplogroups suggesting minimal, if any, impact of ancient nomads of the Eurasian steppe. Fourteen individuals were included in a shared haplotype analysis which revealed that more than half (8/14=57%) of the hypervariable I (HVSI) haplotypes from Samtavro were previously reported in modern day Georgians. Similar haplogroup composition, low Fst values and a high haplotype sharing between ancient Samtavro and modern day Georgians suggests an autochthonous origin of the Samtavro population followed by a high degree of population continuity in the region over the last 1,500 years. However, the mtDNA represents just a single lineage precluding a fuller understanding without the co-analysis of nuclear and Y chromosomal genetic diversity