In this concluding paper of the JONA special volume on the Norse Greenland isotope study, we summarize the archaeological interpretations of the previous, technical papers. The study supports the conclusions and widens the results of our earlier limited study, i.e., that the diet of the Norse Greenlanders became more dependent on marine resources over time. The isotope data provide information at the level of the individual, and the study indicates that the Norse Greenlanders had an isotopically varied diet; there is no evidence that these differences were linked to sex or age. The shift in diet seems to have happened gradually, perhaps beginning during the initial settlement. The swiftness of the change, however, depended on where the immigrants settled; settlers in the southern part of the Eastern Settlement and in the Western Settlement may have adapted to the marine resources more rapidly than those in the central Eastern Settlement region. Social differences may partly explain the isotopically varied diet within Norse society; this explanation is, however, not without its reservations. Despite the changes in the dietary economy, and the increasing dependence on the marine resources, farming strategies remained unchanged. Climate change and unsustainable land-use practices have been proposed as two of the main reasons for the depopulation of the Norse Greenland settlements in the late 1400s, and it is obvious to draw attention to these factors when trying to explain the changes in the dietary economy. It is, however, more doubtful whether the environmental changes were, after all, the sole cause of the depopulation of the Norse Greenland settlement. The Norse Greenlanders apparently adapted well to their physical environment, and they could survive on the marine resources in as far as they were available.