The 82nd Annual Meeting of the American Association of Physical Anthropologists (2013)


Microevolutionary Change in the Human Mandible

DONNA C. BOYD1, CLIFF BOYD1 and WILLIAM L. HYLANDER2.

1Anthropological Sciences, Radford University, 2Dept. of Evolutionary Anthropology, Duke University

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Previous research on craniometric secular change has documented a pattern of increasing cranial vault height, base length, and narrowing of the cranial vault and face in American White and Black crania over the past 150 years. This has been attributed to environmental variables relating to improved nutrition, leading to an extended period for subadult basicranial growth. Concomitant microevolutionary change in American White and Black mandibles has not been fully investigated. This paper compares both linear (n=14) and coordinate (involving 45 landmarks) dimensions from male and female mandibles representing three temporal groups: 1) 19th century Blacks from a combination of several antebellum sites from the mid-Atlantic region; 2) Terry collection Blacks (1828-1924); and 3) a modern sample of Blacks from the Bass Collection. Males and females were separated as to sex. Linear measurements were analyzed via MANOVA (Multiple Analysis of Variance), while the geometric morphometric data underwent standard Procrustes, Thin-Plate Spline, and Principal Coordinate analyses. Results indicate a significant increase in both chin height and ascending ramus height from the 19th to the 20th century samples, while mandibular angle significantly decreases across this transition. Overall, there is a documented increase in mandibular height which appears to parallel that seen in American Black crania. Mandibular secular changes as indicated by the landmark coordinate data analysis (reflecting changes in mandibular shape rather than size) are more complex and are discussed in terms of slavery and other environmental changes affecting American Blacks across this transition.

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