Mitochondrial DNA and Y-chromosomal diversity in ancient populations of domestic sheep (Ovis aries) in Finland: comparison with contemporary sheep breeds

A 523-bp mitochondrial DNA sequence was successfully amplified for 26 of 36 sheep ancient samples i.e. five, seven and 14 samples representative of Iron Age, Medieval and Post-Medieval sheep, respectively. Genetic diversity was analyzed within the cohorts. This ancient dataset was compared with present-day data consisting of 94 animals from 10 contemporary European breeds and with GenBank DNA sequence data to carry out a haplotype sharing analysis. Among the 18 ancient mitochondrial DNA haplotypes identified, 14 were present in the modern breeds. Ancient haplotypes were assigned to the highly divergent ovine haplogroups A and B, haplogroup B being the major lineage within the cohorts. Only two haplotypes were detected in the Iron Age samples, while the genetic diversity of the Medieval and Post-Medieval cohorts was higher. For three of the ancient DNA samples, Y-chromosome SRY gene sequences were amplified indicating that they originated from rams. The SRY gene of these three ancient ram samples contained SNP G-oY1, which is frequent in modern north-European sheep breeds.Our study did not reveal any sign of major population replacement of native sheep in Finland since the Iron Age. Variations in the availability of archaeological remains may explain differences in genetic diversity estimates and patterns within the cohorts rather than demographic events that occurred in the past. Our ancient DNA results fit well with the genetic context of domestic sheep as determined by analyses of modern north-European sheep breeds.Archaeological and molecular genetic evidence suggests that sheep’s (Ovis aries) wild ancestor was the Asiatic mouflon (O. orientalis) and that it was domesticated about 11 000 years ago in the Fertile Crescent region [1]. The genetic history of the domestication of sheep has been investigated by analysing maternally inherited mitochondrial DNA (mtDNA) in modern sheep breeds. To date, five phylogenetically divergent mtDNA haplogroups descending probably