Ancient mtDNA and Migration During the Iron Age
Genome sequencing studies involving ancient human DNA have played a crucial role in uncovering ancient human migration events, processes, and history in Europe and Asia continent. One example of how next generation sequencing technology is of exquisite help to apprehend human history is the genetic studies revealing initial colonization of Europe by modern humans from Romania. However, the human history of Northeastern Europe isn't properly studied due to the shortage of preserved human samples and the lack of genetic statistics from those sites. This is primarily because of the annual repeated freeze-thaw cycles that degrade the DNA present in the bone material. A recent study by the Onkamo group, published in Scientific Reports, involving mitochondrial DNA sequencing revealed the presence of diverse populations and migration of farmers from east of Finland in the closing duration of Iron-Age. The study investigated the mitochondrial DNA diversity of Finland. The large variety of historic human samples collected from Finland and analyzed in the study makes it the largest and most important study so far. The investigators selected Finland for their studies because of divergent population history and also lack of genetic records about prehistoric human populations. Here researchers collected ancient samples and studied the mitochondrial genome diversity linked to hunter-gatherer and agricultural populations. The samples were collected from human remains who lived within the duration of 300-1800 AD. Seventy complete mitochondrial genome samples were gathered from five burial sites, located in Finland from the western coast to Lake Ladoga. Those samples had been originated within the Late Roman Iron Age (300 AD) or Middle Ages (1500 AD). Some other 33 mitochondrial genome samples were amassed from particularly five historical burial sites across southern Finland dated back to 1400-1800 AD. The study, first of all, began with samples from 141 people, but mitochondria were captured for 134 samples and were sequenced. The researchers performed shot read DNA sequencing on mitochondrial DNA using Illumina sequencing platform. Out of 134 samples, 103 samples were selected for further mitochondrial genome sequence analysis. The researchers didn't include 31 samples for their analysis because of excessive contamination and inadequate statistics for those samples. The investigators discovered that historical samples shared mitochondrial heredities with new populace of Finland. The research team categorized the mitochondrial genomes variation from Iron-Age Finland in either hunter-gatherer or agricultural human groups. They observed 95 unique haplotypes from 103 complete sequences. The U haplogroups were associated with hunter-gatherer and H haplogroups had been linked to agricultural populations. Furthermore, variations in haplogroups were observed depending on the ancient sites. The data analysis revealed that hunter-gatherer was linked to southern and southwest Finland, whereas southeastern and eastern Finland was associated with ancient farming groups in the Iron age that's contrary to what is located in modern Finland populace. The analysis suggested that agricultural populations in eastern Finland were possibly due to migration of farmers from the west, south, and east of the country. The authors stated that "the results suggest a late genetic shift from hunter-gatherers towards farmers in North-East Europe." For the reason that mitochondrial DNA in a person comes from the mother, consequently, this study reveals the maternal ancestry of people who lived earlier in that region.