The 81st Annual Meeting of the American Association of Physical Anthropologists (2012)

Shape analysis of the proximal MT 4 and MT 5 articular surfaces


Anthropology, Lawrence University

Saturday All day, Plaza Level Add to calendar

Proximal MT 4 and MT 5 articular surface shapes were analyzed using geometric morphometrics to test the hypotheses that the human articular surfaces are quantitatively different from those of apes, and that there is no difference in articular surface shape between shod and unshod humans. Shod and unshod humans are compared to Pan, Gorilla, and Hylobates. Shod and unshod humans do not have significantly different surface shapes for MT 4 and MT 5, but both are different from the MT 4 shape of all ape groups. The MT 4 analysis shows a highly convex surface in apes, with the surface of Hylobates extending further to the dorsal aspect of this metatarsal. This suggests Hylobates has a greater range of motion at the midfoot break compared to African apes. Gorilla and Pan do not differ significantly from one another in MT 4 surface shape, whereas Hylobates is different from the African apes. The MT 4 fossil specimens OH 8 and Stw 628 show greater morphological affiliation with humans. The MT 5 analysis shows that Pan and Hylobates have a medio-laterally extended and concave articular surface that is convex in the dorso-plantar plane. The human groups are narrower and flatter in the medio-lateral plane, with a smaller degree of dorso-plantar convexity. There is considerable overlap in shape patterns between groups in the MT 5 analysis. The MT 5 fossil specimens AL 333-13, AL 333-78, OH 8, and Stw 114/115 show closer affiliation to humans and Gorilla.

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