Craniofacial growth and development in modern humans and Neanderthals

Landi, Federica

Abstract

This thesis assesses craniofacial growth, development and the dynamics of developmental interactions among cranial regions in modern humans and Neanderthals. To these ends, virtual segmentation, landmarking and Geometric Morphometrics (GM) are applied to an ontogenetic series of the whole crania of 68 H. sapiens and 12 H. neanderthalensis. First, the ontogenetic shape and form changes in the cranial vault, base and face are explored, and the locations and magnitudes of these changes are discussed. Secondly, allometric scaling is tested for differences among different age classes in the three regions of the cranium. In addition, the degree of covariation among these and how it changes over time is investigated.

The study then focuses on interactions among facial regions. First, similar analyses as those used in the study of the cranium are applied to compare growth, development and covariation among parts of the face in different age classes. Additionally, a sample of 227 modern humans from 0 to 6 years of age is analysed using path analysis, to investigate the cascade of interactions and relative contributions of soft tissue and skeletal elements to the overall growth and development of the face. Last, the facial morphology of H. sapiens is compared to that of H. neanderthalensis and their ontogenetic trajectories are tested for divergence. Novel method registration-free colour maps are used to visualise regional changes during growth and development and to compare the morphologies of the two species. Covariation among facial elements is also compared to assess potential differences in developmental interactions. In modern humans, the results show that allometry and covariation change significantly among age classes and between cranial regions during ontogeny and that covariation is stronger in younger subadults than in older subadults and adults. Among modern humans, significantly divergent trajectories are observed between age classes during ontogeny in all three cranial regions. In the modern human face, allometric scaling also differs among age stages in each region. Interestingly, covariation among facial regions becomes progressively non-significant with time, with the exception of those including the nose and maxilla. Path analysis in modern humans shows a large contribution of the proxy used for nasal septum to the overall facial development. Soft tissues contribute only locally to the development of some skeletal elements of the face. Major aspects of the differences between adult modern humans and Neanderthals are already present in the youngest individuals. However, additional differences arise through differences in the degree of change in facial size and significantly divergent allometric trajectories. Analyses of covariation among Neanderthal facial regions suffer from small sample size but, where significant, suggest that the interactions among cranial components are similar to those in modern humans, with some differences.

Citation

Landi, F. (2020). Craniofacial growth and development in modern humans and Neanderthals. (Thesis). Hull York Medical School, the University of Hull and the University of York. Retrieved from https://hull-repository.worktribe.com/output/4222958

• Thesis Type: Thesis
• Deposit Date: Mar 11, 2021
• Publicly Available Date: Feb 23, 2023
• Keywords: Medicine
• Public URL: https://hull-repository.worktribe.com/output/4222958
• Additional Information: Hull York Medical School, The University of Hull and the University of York
• Award Date: Jul 1, 2020