An archaeological survey of Kitsissut, a remote island cluster in the High Arctic of Kalaallit Nunaat (Greenland), has revealed a human presence almost 4500 years ago, during the formation of a vital marine environment—Pikialasorsuaq polynya. Kitsissut is accessible only by a difficult open-water journey, and repeated occupation thus permits inferences on the sophistication of watercraft technology and navigational skill. Here, the authors argue that this demonstrable reach of Early Paleo-Inuit communities across marine and terrestrial ecosystems enhances our understanding of their lifeways and environmental legacy, raising critical new questions about Indigenous agency in shaping emerging Arctic ecosystems.