The Functional Significance Of Neanderthal Pubic Morphology (human Evolution, Pelvis, Hominidae).

Abstract

The superior pubic ramus in Neandertals is elongated medial-laterally and thinned dorsal-ventrally compared to more recent humans. In the past, this morphology has been treated as a taxonomic marker distinguishing Neandertals from anatomically modern humans and recent humans and as evidence for a fundamental shift in reproductive pattern in the transition from Neandertals to modern humans. This study tests the hypothesis that interpopulation variation in the length of the pubic bone (among recent humans and between Neandertals and anatomically modern humans) is related to body proportions. Because maternal weight is an important factor in determining infant size, and because Neandertals were heavy, stocky, muscular individuals, they would have had large infants and as a result of selection during childbirth, should have enlarged birth canals and elongated pubic bones. Data were analyzed from skeletal samples from nine recent human populations which span a wide range of variation in stature and weight in order to examine the relationships between these variables and pubic length. The proposed relationship between body proportions and pubic length was found to occur among recent human populations and is suggested to account for Neandertal pubic length as well. Neandertal females who were very heavy compared to recent human females fall at the upper extreme of the recent female range of femoral head diameters but within the expected range of pubic length for recent females at that predicted body weight. This suggests that maternal:infant size relations in Neandertals were not significantly different from those in recent humans. Neandertal males, on the other hand, had considerably greater pubic lengths than would be predicted for recent human males of their body weight. In contrast to the general human pattern, Neandertal males had longer pubic bones than Neandertal females. This is shown here to be related to the extreme sexual dimorphism in body weight seen in the Neandertal specimens included in this analysis. In both pubic length, and sexual dimorphism in pubic length, Neandertals follow the same allometric relationships as recent humans. These characteristics are the result of their body proportions and level of sexual dimorphism in body weight as they are in recent humans. This study provides no evidence of a discontinuity between Neandertals and more recent humans in skeletal features associated with the human adaptation to parturition.