In this communication, we present the results of a 3D geometric morphometric analysis of the cranial base variations in living and fossil Hominoidea. A number of studies on cranial base morphology have dealt with basicranial flexion, mainly in relationship with cranio/facial size and shape (Bastir et al., 2010; Bastir et al., 2011; Lieberman, 2011). By contrast, our aim is to test to what extent basicranial morphology is related to functional and/or ontogenetic patterns. Particularly, we are interested in the evaluation of factors that may have influenced the cranial base morphology in Plio-Pleistocene Hominins. We used a configuration of 18 landmarks distributed on the cranial base on a sample of 128 specimens (infants, juveniles, and adults) of Homo, Australopithecus, Paranthropus, Pan, Gorilla, and Pongo; the age at death of the specimens was determined by patterns of molar eruption. The landmark set has been transformed into shape coordinates by generalized Procrustes analysis and the variance-covariance matrix was explored through principal component analysis (PCA). Shape predictions were performed by regression of the PC scores on the centroid size in order to display the respective pattern of growth within the different OTUs. The results discriminates two main ontogenetic series independently from phylogenetic/taxonomic relationships. The distribution of these clusters in the morphospace may be viewed in relationship with ontogenetic trajectories as well as with posture and locomotion. Pongo, Gorilla, and Pan, share a common pattern of cranial base variation during growth, whereas modern humans show a different pattern of change with analogous ontogenetic polarity, shared with Mid-to-Late Pleistocene Homo. Australopiths and early-Homo specimens occupy a morpho-space that is distinct from both the other Homo, representatives and living great apes, while approach the ontogenetic series of the formers. It is worth mentioning that this is not in relationship with their degree of encephalization, but it is consistent with the Anova (p < 0.001) performed on PC scores on posture and locomotion variables. When dealing with shape predictions, the P-values of the regression analysis of size related trajectories are statistically significant for the extant Hominoidea, while adult Australopiths and early Homo, are closer to the trajectories of both modern humans and Mid-to-Late Pleistocene Homo, (including Neanderthal juveniles) than to those of great apes. The phenetic relationships based on UPGMA cluster analysis (adult samples only) further demonstrate the independence of the observed patterns of cranial base morphology from phylogenetic/taxonomic relationships. References:Bastir, M., Rosas, A., Stringer, C., Cuétara, J.M., Kruszynski, R., Weber, G.W., Ross, C.F., Ravosa, M. J., 2010. Effects of brain and facial size on basicranial form in human and primate evolution. J. Hum. Evol., 58, 424-431. Bastir, M., Rosas, A., Gunz, P., Pena-Melian, A., Manzi, G., Harvati, K., Kruszynski, R., Stringer, C., Hublin, J-J., 2011. Evolution of the base of the brain in highly encephalized human species. Nat. Commun., 2, 588. (doi:10.1038/ncomms1593) Lieberman, D.E., 2011. The Evolution of the Human Head. Cambridge, MA: Harvard University Press.

Cranial base variations in extant Hominoidea and fossil Hominins

PROFICO A;
2013-01-01

Abstract

In this communication, we present the results of a 3D geometric morphometric analysis of the cranial base variations in living and fossil Hominoidea. A number of studies on cranial base morphology have dealt with basicranial flexion, mainly in relationship with cranio/facial size and shape (Bastir et al., 2010; Bastir et al., 2011; Lieberman, 2011). By contrast, our aim is to test to what extent basicranial morphology is related to functional and/or ontogenetic patterns. Particularly, we are interested in the evaluation of factors that may have influenced the cranial base morphology in Plio-Pleistocene Hominins. We used a configuration of 18 landmarks distributed on the cranial base on a sample of 128 specimens (infants, juveniles, and adults) of Homo, Australopithecus, Paranthropus, Pan, Gorilla, and Pongo; the age at death of the specimens was determined by patterns of molar eruption. The landmark set has been transformed into shape coordinates by generalized Procrustes analysis and the variance-covariance matrix was explored through principal component analysis (PCA). Shape predictions were performed by regression of the PC scores on the centroid size in order to display the respective pattern of growth within the different OTUs. The results discriminates two main ontogenetic series independently from phylogenetic/taxonomic relationships. The distribution of these clusters in the morphospace may be viewed in relationship with ontogenetic trajectories as well as with posture and locomotion. Pongo, Gorilla, and Pan, share a common pattern of cranial base variation during growth, whereas modern humans show a different pattern of change with analogous ontogenetic polarity, shared with Mid-to-Late Pleistocene Homo. Australopiths and early-Homo specimens occupy a morpho-space that is distinct from both the other Homo, representatives and living great apes, while approach the ontogenetic series of the formers. It is worth mentioning that this is not in relationship with their degree of encephalization, but it is consistent with the Anova (p < 0.001) performed on PC scores on posture and locomotion variables. When dealing with shape predictions, the P-values of the regression analysis of size related trajectories are statistically significant for the extant Hominoidea, while adult Australopiths and early Homo, are closer to the trajectories of both modern humans and Mid-to-Late Pleistocene Homo, (including Neanderthal juveniles) than to those of great apes. The phenetic relationships based on UPGMA cluster analysis (adult samples only) further demonstrate the independence of the observed patterns of cranial base morphology from phylogenetic/taxonomic relationships. References:Bastir, M., Rosas, A., Stringer, C., Cuétara, J.M., Kruszynski, R., Weber, G.W., Ross, C.F., Ravosa, M. J., 2010. Effects of brain and facial size on basicranial form in human and primate evolution. J. Hum. Evol., 58, 424-431. Bastir, M., Rosas, A., Gunz, P., Pena-Melian, A., Manzi, G., Harvati, K., Kruszynski, R., Stringer, C., Hublin, J-J., 2011. Evolution of the base of the brain in highly encephalized human species. Nat. Commun., 2, 588. (doi:10.1038/ncomms1593) Lieberman, D.E., 2011. The Evolution of the Human Head. Cambridge, MA: Harvard University Press.
2013
2195-0784
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11568/1148546
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