ABSTRACT
Neandertals and Homo sapiens are known to differ in scapular glenoid fossa morphology. Functional explanations may be appropriate for certain aspects of glenoid fossa morphology; however, other factors--e.g., allometry, evolutionary development--must be addressed before functional morphology is considered. Using three-dimensional geometric morphometrics, shape of the scapular glenoid fossa was compared among Neandertals, early and recent modern humans, chimpanzees, orangutans, Australopithecus afarensis, and Au. sediba. Permutation analysis revealed that side, sex, and lifestyle did not correlate with shape. Of the features we found to differ between groups, anterior glenoid rim morphology and fossa curvature did not correlate with the aforementioned shape variables; thus, a functional explanation is appropriate for these components of glenoid fossa shape. Shared morphology among recent humans and chimpanzees (to the exclusion of Neandertals and orangutans) suggests independent forces contributing to these morphological configurations. Potential explanations include adaptations to habitual behavior and locomotor adaptations in the scapulae of recent humans and chimpanzees; these explanations are supported by clinical and experimental literature. The absence of these morphological features in Neandertals may support the lack of these selective forces on their scapular glenoid fossa morphology.
Subject(s)
Biological Evolution , Glenoid Cavity/anatomy & histology , Glenoid Cavity/physiology , Mathematics , Neanderthals/anatomy & histology , Neanderthals/physiology , Adaptation, Physiological/physiology , Animals , Biomechanical Phenomena/physiology , Humans , Imaging, Three-Dimensional , Locomotion/physiology , Pan troglodytes/anatomy & histology , Pan troglodytes/physiology , Pongo/anatomy & histology , Pongo/physiology , Principal Component AnalysisABSTRACT
The evolution of the human upper limb involved a change in function from its use for both locomotion and prehension (as in apes) to a predominantly prehensile and manipulative role. Well-preserved forelimb remains of 1.98-million-year-old Australopithecus sediba from Malapa, South Africa, contribute to our understanding of this evolutionary transition. Whereas other aspects of their postcranial anatomy evince mosaic combinations of primitive (australopith-like) and derived (Homo-like) features, the upper limbs (excluding the hand and wrist) of the Malapa hominins are predominantly primitive and suggest the retention of substantial climbing and suspensory ability. The use of the forelimb primarily for prehension and manipulation appears to arise later, likely with the emergence of Homo erectus.
