Each of us tells a story about who we are, often tracing our identity back through an imagined line of ancestors. Though identity is fundamentally cultural, we tend to anchor it in biology – in the idea of a stable genetic inheritance passed down through generations. Population genomics has exposed a history far more complex, dynamic and intertwined than we might wish to imagine. Even in a place such as Britain, long imagined as an island of deep and uninterrupted heritage, genetic data suggest