The 84th Annual Meeting of the American Association of Physical Anthropologists (2015)

Integration Magnitudes and Patterns in Human and Great Ape Mandibles


Anthropology, University of Florida

March 27, 2015 , Archview Ballroom Add to calendar

Magnitudes and patterns of integration have important effects on both the evolutionary trajectories of biological structures and the availability of morphospace for those same structures. While human mandibles are proportioned significantly different from those of the other great apes, a comparative investigation of integration in these structures has yet to be undertaken. Based on 16 linear and angular measurements from Pan (N=92), Gorilla (N=94), Pongo (N=87), and Homo (N=94), species variance-covariance matrices (VCVs) were produced. Simulated selection vectors were pushed through the VCVs to measure how the vectors were deflected, recording several integration statistics. Hominids do not appear to have significantly different magnitudes of integration (evolvability statistic: Homo=0.013, Pan=0.017, Gorilla=0.011, Pongo=0.015). Furthermore, preliminary analyses of the patterns of integration (evolutionary distance statistic: Homo-Pan: 0.008, Homo-Gorilla: 0.007, Pan-Gorilla: 0.013) indicate humans possess an intermediate pattern to that of chimps and gorillas, but more similar to either species than chimps and gorillas are to each other. These results suggest that the human mandible was not dramatically reorganized in order to achieve its unique position in morphospace. This has important implications for appreciating the selective agents that produced the much shortened, more arched, and chinned human jaw.