The 81st Annual Meeting of the American Association of Physical Anthropologists (2012)

Integration and hominoid sexual dimorphism


Anthropology, University of Arkansas

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Cranial integration studies in hominoids have focused on either one sex, or in removing aspects of size in order to combine sexes. However, these approaches tend to discount or deemphasize the role size and sexual dimorphism may have played in cranial evolution. To date, the hypothesis that a sexually dimorphic species displays alternate integration patterns has not been tested. If sexual dimorphism does not affect integration patterns, then mixed-sex samples could be used; this would greatly increase the likelihood of investigating integration in the fossil record, through increased sample-size. 14 cranial measurements were taken on 59 adult male and 53 adult female gorillas, encompassing an equal distribution of neurocranial and facial measurements and in all three dimensions, so as to not bias the results in any one anatomical unit or plane. Integration was quantified in these samples using conditional independence modeling. Results of these analyses indicate that male and female gorillas are characterized by overall different patterns of cranial integration. Both sexes, however, do share the condition of integration within the cranial vault. This indicates that the current strategy of separating out males and females in integration studies, or removing the effects of size and relying on shape only, is the most effective choice; mixed-sex samples of highly sexually dimorphic species are likely to give a skewed result that does not reflect the actual patterns of integration seen in either sex, and as such, would not prove useful in studying patterns of integration.

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