Quantitative discrimination of deformation in Fueguian crania

Abstract

Objectives: Artificial deformation of the cranium in humans has been related to powerful environmental-cultural stimuli that modify vectors of growth and development when the cranium is still malleable. Osteological differentiation into deformed and nondeformed remains enables the morphological information of individuals that make up ethnic groups or populations to be separately contrasted, the invariant measurements of deformation to be identified, the information provided by archeological remains to be placed in a social context, the cranial variation to be related to genetic variation (individuals without deformation), and predictions to be made (in the absence of direct genetic information). Methods: With samples of reduced size and many variables, we propose a decision rule based on: (a) pre-selecting variables (Kruskal-Wallis and Λ-Wilks test); (b) applying logistic regression to obtain the optimal classification criterion; and (c) defining a multi-criterion decision rule to bring about greater robustness. Results: After applying the decision rule to a sample of 180 crania (71 from the Selknam, 74 from the Yamana, and 35 from the Alakaluf ethnic groups), it was possible to identify the Selknam men with frontal deformation and the Yamana women with flattening of the parietal regions at the height of the bregma. Conclusions: From there on with the information provided by the graphical representation of the populations in the most informative dimensions and the homogeneity contrast between sexes, we related the frontal deformation in Selknam men to dragging firewood, vegetable matter, domestic utensils, and heavy pieces of meat from the hunt. On the other hand, the flattening of the parietal areas at the height of the bregma in Yamana women is related to loading and transporting vegetables and animals in baskets or leather sacks. K E Y W O R D S deformed skulls, Fuego-Patagonians, logistic regression FIGURE 1 Main sites of Tierra del Fuego and South Patagonia showing the diversity of crania, modified or not, by sexes. For more detailed information (only for current Chilean territory), see Alfonso-Durruty et al. (2015). Circles: female; triangle: male. Diamond: Not deformed. In black: with deformation LUCEA ET AL.

Functional Adaptation of the Human Facial Skull to the American Ecosystems of the Late Pleistocene

“…Cases that were doubtful in terms of gender and ethnic group were diagnosed with discriminant functions taken from well documented specimens. Deformed crania were detected and discarded [18,19], since deformation causes changes to the face and the base of the cranium [16,17,28]. Seventeen facial variables were selected from the 63 craniofacial variables that were initially available, to make the multivariant analysis less difficult to interpret.…”

“…The first one is intentional or unintentional cranial deformation, which is very common in American cultures. Slight cases of this process often go unnoticed [16][17][18][19]. Secondly, the correct diagnosis of gender, which requires quantitative criteria, preferably quantitative and specifically generated for the group being studied [20].…”