Objectives: Nineteenth and twentieth century documents testify that four ethnic groups, generally classified as terrestrial hunters or canoe nomads, inhabited Fuego-Patagonia. Archaeologically, however, their presence and temporal depth remains unknown. This study analyzes the antiquity and geographic distribution of cranial modification, a highly visible symbol of social identity, in Fuego-Patagonia, Chile, to assess whether it expressed ethnic affiliation. Materials and Methods: A total of 60 adult skulls from Southern Patagonia (n532; 53.3%) and Tierra del Fuego (n528; 46.7%) were examined for age-at-death, sex and cranial modification with standard methods. Individuals were further categorized as terrestrial (n526; 43.3%), marine (n521; 35%) or indetermined hunter-gatherers (n513; 21.7%) based on the archaeological site's characteristics, geographic location, and isotopic information. Results: Thirty percent (n518) of the skulls in this study were modified, and most of the modified skulls (n515) presented a tabular-erect shape. No statistically significant differences were identified between Fuegians and Patagonians, males or females, or between the different types of adaptation and geographic locations. Discussion: Thus, this Late Holocene, widely distributed practice, was not a reflection of ethnicity, but a material expression of information circulation and the complex social relations that these small-size groups had with one another. These results suggest that the emergence of modern ethnic identities in the region is a historic process that resulted from the interaction of local groups with European and Criollos. [ABSTRACT FROM AUTHOR]