Palatine (PT) and mandibular torus (MT) have long been of interest to dental researchers and anthropologists, but their aetiology remains unresolved. Some combination of genetic and environmental factors influences their expression, but the relative role of each remains contentious. Previous research has shown that the Greenlandic Norse exhibit exceptionally high frequencies and pronounced expressions of PT and MT. In this regard, they are significantly different from genetically related medieval Scandinavian populations, so environmental factors have to be considered. An earlier study that estimated stable carbon and nitrogen isotope compositions for a Greenlandic Norse sample makes it possible to compare directly PT and MT expression with the relative degree of marine protein intake. For comparative purposes, parallel observations were made on a Greenlandic Inuit sample. Some researchers suggest the intake of marine resources could impact bone development, including torus expression, but our analysis found no significant correlation between PT or MT expression and δ¹³C and δ¹⁵N values in the Norse. In the Inuit, PT expression also showed no relationship to stable isotope compositions. MT size in the Inuit did, however, show a significant inverse relationship with δ¹³C and δ¹⁵N values. As MT size goes up, stable isotope compositions go down. Compared with contemporary European populations, the Greenlandic Norse show very positive isotope compositions, but the Inuit, with their high protein-high fat diet, show significantly higher δ¹³C and δ¹⁵N values than the Norse. It is unclear how this relates to the contrasting findings for MT size and stable isotope values.