What Just like humans, individual animals may disperse from the place they were born to explore new habitats, while others never leave the place they were born. The "Pioneers" project aims to understand what makes such pioneer animals leave, how they disperse to new niches and habitats, and what role the genome plays in determining whether pioneer animals are successful or go extinct, and thus potentially change the history of their species. This is one of the great, unanswered questions in biology, and has implications for conservation of biodiversity in a world were species ranges are changing rapidly due to environmental change and human impacts. Why The Ocean covers 2/3 of the Earth, yet we know surprisingly little about even the basic principles of distribution and evolution of marine biodiversity. The project addresses this knowledge gap by describing the genomic basis of animal dispersal and response to environmental and human pressures, and thereby to understand why some species successfully expand to new areas, while others fail and become extinct. The novel and interdisciplinary framework to generate and combine telemetry data, genomics and ancient DNA will constitute an important scientific resource and may inspire similar efforts to understand the distribution of Earth's biodiversity. How The "Pioneers" project consists of three independent yet synergistic subprojects that utilizes a unique suit of satellite telemetry data, DNA and zooarchaeological material from two widespread marine mammal species; the harbour porpoise and harbour seal. Subproject 1 will combine telemetry and genome data to investigate the genomic background driving some animals to disperse, while others stay where they were born. Subproject 2 uses genomic data to assess the consequences, drivers and timing of the two species' range expansion across the northern hemisphere. Subproject 3 will obtain and analyse ancient DNA to understand the origin and fate of the first pioneer harbour seals and porpoises that colonised Denmark shortly after the last glacial period. SSR In a world where species ranges are changing rapidly due to global warming and pressures from human activities, fundamental insights on the drivers and genetic traits of animal dispersal and adaptation are crucial for identifying and protecting the populations and species that may not possess the versatility and adaptive potential to survive the biodiversity crisis. The project outcomes will provide direct scientific advice for policy makers, NGOs and societies concerned with the impacts of ongoing environmental change and human activities. This is in line with UN, EU and other organisations' top priorities to improve the biodiversity, health and sustainable use of the world's seas, including the "Blue Economy", "Ocean Decade" and "Sustainable Development Goals" initiatives.