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Adaptation and Demographic Processes in Ukraine from the Mesolithic to the Present

Periodic Reporting for period 1 - UkrAD (Adaptation and Demographic Processes in Ukraine from the Mesolithic to the Present)

Berichtszeitraum: 2021-06-01 bis 2023-05-31

Migration, admixture and natural selection have been a major factors shaping human societies and genomes through time. Ancient DNA research indicates that, by-and-large, the genomes of present-day Europeans comprise ancestries from three major layers of people: local hunter-gatherers, Near Eastern early farmers, Steppe pastoralists. However, the detailed genetic history of any given area is always much more complex, calling for more focused and local-scale studies. One such relatively understudied region is present-day Ukraine. Southern Ukraine, as part of the Eurasian Steppe, has been in the path of several migrating groups, e.g. Yamnaya Steppe pastoralists, mixed-origin Cimmerians and Scythians, Gothic Chernyakhov people, Iranian Alans, Golden Horde Mongols, Turkic Nogais, Slavic Cossacks.
It is important to study demographic history to gain insight into migrations and admixture events in the past to help us understand how these processes have shaped genomes and societies and influenced how today's populations have come to be. Also, tracing the drivers of natural selection in the past can shed light on how changes in the environment (both natural and societal) have led to phenotypic changes in humans which in turn can provide clues for how we might respond to the changing environment in the future.
The main research objectives of the project were to generate genomic data from individuals from the Neolithic to the Middle Ages in order to shed light on patterns of genetic variation in Ukraine through time, to characterize the composition of their ancestries and interpret the results in the context of archaeological and historical information in order to understand the demographic history of the area, and to compare hypothesized ecological drivers of selection using a range of ecological proxies in a likelihood framework in order to pinpoint the drivers of selection. Futhermore, the objective of this project is for the researcher to mature to be independent by developing excisting and acquiring new skills – furthering her skills in her current research area of demographic history inference and expanding into a new field of studying natural selection, as well as developing transferable skills by conceiving and managing a project, disseminating and communicating the project results, networking, and supervising students.
The main research conclusion of the project is that there has been a lot of genetic variability in Ukraine through time, especially during the Iron Age and the Middle Ages. What is more, the researcher has developed and acquired skills both directly related to research as well as transferable skills and has matured into an independent scientist who is ready to apply for further funding and conduct high-quality research as a principal investigator.
All available samples were processed in the ancient DNA laboratory and screened for human ancient DNA and later, additional sequencing data was generated for individuals with sufficiently high levels of preserved human DNA.
A dataset including the new data and comparative data from modern and other ancient populations was compiled and demographic history was inferred using a multitude of analyses. It was seen that there has been a lot of genetic variability in Ukraine through time, especially during the Iron Age and the Middle Ages. A draft of the manuscript has been put together and will be submitted for publication soon.
Several new papers have become available where signals of selection have been estimated over long periods of time and large geographic areas – it was decided that variants associated with immunity that were detected as having been under selection in those papers will be used in this project. Potential proxies for drivers of selection on variants associated with immunity were discussed and a suitable dataset was chosen. Likelihood-based analyses to identify which ecological variables best explain allele frequency trajectories of the chosen immunity-related variants are under way and a manuscript will be put together shortly.
The data generated as part of the project will be made publicly available under European Nucleotide Archive accession number PRJEB64640 as soon as the results on the demographic history of Ukraine are published in a journal. This allows for the data to be used in future research by anyone. The low amount of data previously available from Eastern Europe makes it a valuable resource to the field of aDNA research. What is more, the field is still constantly developing so new methods can be applied to the data in the future to further scientific knowledge as much as possible with the data available. Furthermore, Pooja Swali from Dr. Skoglund's team detected pathogens in several of the samples, which are already being studied further in collaboration with Dr. Marcel Keller (University of Bern, University of Tartu) and Dr. Meriam Guellil (University of Vienna).
The project results were presented at the 28th European Association of Archaeologists Annual Meeting, the EMBO | EMBL Symposium "Reconstructing the human past: using ancient and modern genomics" and the Society of Molecular Biology and Evolution Annual Meeting 2023. Furthermore, the results were presented at the University of Tartu Institute of Genomics monthly pizza seminar, the Uppsala University Network on Indo-European Studies of Cultures, Languages and Traditions workshop "The earliest steps from the steppes – archaeology and aDNA in the Great Steppe" and the Scuola di Genetica in Cortona summer school "The ancient DNA revolution: from the initial attempts to the Nobel Prize".
Prior to this project, there was limited ancient data available from Ukraine overall and only one individual with genome-wide data from the Middle Ages – a situation which has been greatly remedied by this project. Furthermore, this project has revealed a level of genetic heterogeneity within several archaeological groups and through a long period of time (Iron Age and the Middle Ages) which has not been shown in Europe before.
The expected result of the adaptation part of the project is pinpointing the ecological drivers of selection on immunity related variants in Ukraine and in Europe more widely.
The project results have been communicated to members of the general public at Pint of Science 2023 in London, UK, and to the Hugo Treffner Gymnasium history club members in Tartu, Estonia. When the results will be published, they will be communicated through social media (Twitter) and through media outlets in the UK, Ukraine and Estonia.
The societal implications of the project results are great, especially given the current situation in Ukraine. The results show that the territory of Ukraine has been home not only to people from many different cultures (which was already known before), but with extremely variable genetic backgrounds, with ancestry from different areas in Europe, the Near East, the Caucasus, Central Asia and East Asia. This shows that the area has been a hotbed of migration and no country should claim "historical unity" with Ukraine as the rationale for forcefully trying to merge.
Tooth of a Scythian Culture associated individual that was sampled for ancient DNA analyses
Researcher Lehti Saag presenting the results of the project at Pint of Science
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