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


Geometric morphometric assessment of pelvic sexual dimorphism in Pan, Gorilla, and Homo sapiens

RONDA R. GRAVES.

Interdepartmental Doctoral Program in Anthropological Sciences, SUNY Stony Brook

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Pelvic sexual dimorphism is closely linked to obstetric requirements in modern humans. Female pelvic morphology evolved to accommodate the delivery of neonates with head circumferences approximating the dimensions of the pelvic inlet, while human males and African apes of both sexes faced no such requirement. Early literature reported sexual dimorphism in the pelves of chimpanzees, but many recent studies refuted these initial claims. This study addresses these contradictions, using qualitative character states and three-dimensional landmark data to record and describe the shape of pelvic morphology specifically linked to obstetrics (the focus of most previous studies) and morphology that is presumably unrelated. Geometric morphometric techniques are used to assess a large sample of African ape and modern human pelves. Principal components analyses effectively separate chimpanzees and humans by sex, but gorilla specimens overlap in shape space. Canonical variates analyses successfully assign all specimens to the correct sex category for each species. Pairwise analyses of regression coefficient vector angles suggest significantly different patterns of variation between humans and chimpanzees and between humans and gorillas, but not between chimpanzees and gorillas. Character states for five qualitative traits used in forensic studies to sex human pelves are considered in African ape pelves. Analysis of these character states fail to separate male and female apes. Many of the sexually dimorphic characters identified in African ape pelves appear to be unrelated to parturition, requiring further examination in the context of phylogenetic history and functional morphology to elucidate the underlying explanations for their presence.

This material is based upon work supported by the National Science Foundation Graduate Research Fellowship under Grant No. 2008071230.

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