LIFETIMES · A Thousand Years of Transformation: Building a genomic bridge between population and life history at the edge of medieval Europe.

Population history is built on individual lifetimes. Life traits such as health, mobility and fertility determine demographic trajectories. Demography, in turn, drives environmental, cultural and biological change, altering future life histories. To unravel these complex feedback loops is to learn where our societies and genomes came from, and where we might go next. Central to these endeavours is the reconstruction of local demographic histories from the archaeological record, which can reveal long-term cycles of growth, decline and transformation. These reconstructions can be built from the top-down (charting macro trends in human activity) or bottom-up (characterising bioarchaeological traits). Ancient genomics promises to transform these dual approaches and further build a bridge between the two, but this requires highly focused regional sampling and methodological innovation. LIFETIMES will build this bridge for one of the world’s most highly-resolved archaeological records - that of medieval Ireland. Leveraging almost 5,000 ancient and modern genomes, it will map in unprecedented detail islandwide and subregional patterns of population size, gene flow and adaptation. These macro-histories will be set against the stories of three communities, whose burial grounds remained in use for almost a millennium. Through exhaustive sampling, extensive family trees will emerge, allowing us to view the longue durée of human history at the highest resolution - as a series of interconnected lifetimes. Changes in social organisation, lifespan and health will be interrogated at the level of the genome, methylome and microbiome. Combined with structured interdisciplinary collaboration, this will be the first such synthesis of its kind. It will not only address longstanding issues within insular history (e.g. language origins, disease risk, past pestilence, gender dynamics), but provide fresh insights into the fundamental interactions between genes, culture and the environment.