Tatiana Malherbe
By analyzing ancient DNA, population genetics makes it possible to follow the migrations of peoples throughout history. A study published in February in PLOS Genetics addressed the case of the peoples of northwest Russia. Surprisingly, it appears that the population currently living in this territory is not descended from the indigenous peoples who lived there between 3,500 and 7,500 years ago and who had already migrated from Siberia. It is likely that this rather hostile region is a place that humans have flowed in and out of for thousands of years.
This article is a translation of “La génétique au service de l’histoire”. It was translated from French by Timothée Froelich.
Population genetics makes it possible to study groups of people and their origins. It is based on the increasingly widespread use of ancient DNA from human remains found across the world.
Samples of contemporary and ancient DNA tested across Eurasia.
Adapted from PLoS Genet 9(2): e1003296. Doi: 10.1371/journal.pgen. 1003296
Earlier this year in PLOS Genetics [available on MyScienceWork], a team of Russian, German and Australian researchers, supported by the scientific consortium of the Genographic Project, stepped back in time in an attempt to understand population movements in the northwest of Europe since prehistoric times. This study used mitochondrial DNA, also known as mtDNA, which is inherited solely from the mother and is present in cells in greater amounts than nuclear DNA. The mtDNA analyzed was extracted from the teeth of 74 skeletons found in northwest Russia, on two 7,500-year-old archeological sites and one dating back 3,500 years. The mtDNA was compared to that of other, more recent or currently living Eurasian peoples. Researching particular mutations in specific regions of the mtDNA makes it possible to characterize individuals and follow the genetic mixing over time. In this case, only the most recent remains could be proved to originate from central or eastern Siberia. As for the oldest ones, it would appear that they come from western Siberia, but specific data is still needed to be sure. According to the researchers, this reveals a genetic discontinuity between prehistoric populations. This can be explained by the small size and the isolation of the groups found in these hostile regions, resulting in the loss of genetic heritage due to an insufficient number of descendants. As Professor Gronenborn, co-author of the article, stresses, we need more data, and time-related data, in particular, to get a better understanding of the migratory flows since prehistory.
The scientists also addressed the case of the Sami people, commonly called Lapps, who live in an area stretching over the northern regions of Sweden, Norway, Finland and Russia’s Kola Peninsula. These people, unique in Europe, possess a limited genetic diversity and mtDNA lines that are very rare in other European populations. According to this recent study, these characteristics do not match with the ancient DNA samples from human remains found on their territory. This proves that the Lapps do not descend from the indigenous people of that time, nor from the populations that came from the area of Poland at the beginning of the Holocene (around 11,000 years BP). But where do the ancestors of the Lapps come from, then? The more likely hypothesis is that they came from the west and, more precisely, from Norway.
Alexandre Ribéron, a lecturer at the University Paul Sabatier, has developed an interest in the evolutionary history of populations. According to him, the study’s results are “a good example of all the gene flows that have shaped human populations since there have been humans on Earth. They show how important migrations were in prehistoric times and in inhospitable areas.” This sort of work is limited by the lack of available samples: skeletons are quite rare to find and the quantities of DNA are low. This justifies the use of mtDNA, which is more abundant and better preserved than nuclear DNA. In addition, as the mtDNA is inherited solely from the mother, we can only obtain a skewed vision of history. It has already been observed that some social systems drove men and women to follow different paths. Only the DNA analysis of the Y chromosome, found only in males, could provide answers to this question.
Ancient DNA makes it possible to rebuild the complex genetic history of populations and to reveal their migratory movements. Accumulating genetic data will help us to understand the relations between different peoples, both in time and in space.
To find out more:
"Ancient DNA: the first three decades", scientific discussion meeting at The Royal Society, 18 November 2013
http://royalsociety.org/events/2013/ancient-dna/
