Keywords

Paleoanthropology, human evolution, facial form, orthognathism

Subject Categories

Anatomy | Evolution | Human and Clinical Nutrition

Abstract

The evolution of the orthognathic condition in the genus Homo represents a monumental transition toward the facial morphology of modern humans from that of earlier hominins, but the phylogenetic positioning of this transformation remains poorly understood. This study investigated temporal trends in maxillary and mandibular prognathism in the genus Homo, and whether maxillary and mandibular shortening in East Asian H. erectus and later East Asian Middle Pleistocene Homo (e.g., Homo longi) represent independent derivations of orthognathic morphology, thereby making orthognathism a homoplasy in the genus Homo. Using a sample of roughly 109 cranial and mandibular specimens spanning the Pleistocene, existing and novel osteometrics were used to assess temporal and geographic trends in prognathic morphology in Homo. Subsequent analyses explored temporal trajectories of facial morphology through principal component and non-parametric statistical analyses and tested the taxonomic affinities of East Asian specimens via distance-based and discriminant classification approaches. It was found that: 1) a progressive reduction in facial projection occurred across populations of Homo throughout the Pleistocene, with a trend of reduced postorbital constriction occurring alongside decreased nasoalveolar clivus projection, 2) several H. longi specimens independently derived orthognathic morphology due to reduction of facial height across varied regions of the face facial proportions, 3) the morphological affinity of H. longi mandibles stood in discrete contrast to their cranial morphological affinity, indicating a notable extent of modularity in this transition. The results of this research should contribute to debates surrounding the taxonomy of Middle Pleistocene hominins and the extent of convergent evolution in the hominin lineage.

Completion Date

2026

Semester

Summer

Committee Chair

Freidline, Sarah

Degree

Master of Arts (M.A.)

College

College of Sciences

Department

Anthropology

Format

PDF

Document Type

Thesis

Language

English

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