Biology Reference
In-Depth Information
FIGURE 12.6
Group mean
configuration (Euro-American and
African-American male) overlays
from superior view. Euro-American
landmarks are represented by open
circles and African-American land-
marks are represented by solid
circles.
male mean. In the face, the more anteriorly positioned subspinale and the more laterally posi-
tioned alares, dacryons, and other facial landmarks suggest a wider mid-face region and
overall broader face in the African-American male mean.
The presence of shape variation in these landmarks of the face and vault for these two
American populations contributes to the ability of statistical programs to distinguish
between these groups based on craniofacial dimensions; however, we are just beginning to
understand the reasons for this pattern of variation. Climatic adaptation has been considered
as an explanation for these differences and may very well hold true for the nasal and mid-
face region (see the review of
Noback et al., 2011
later in this chapter). Nevertheless, research
has also demonstrated secular change in craniofacial form for both Euro-Americans and
African-Americans (see review of
Wescott and Jantz, [2005]
later in this chapter as well as
Jantz and Meadows Jantz [2000] and
Jantz [2001]
). While these trends have been docu-
mented, the reasons (environment, gene flow, or some combination) have not been
completely elucidated; therefore, assigning explanations to the variation depicted in this
mean shape configuration overlay is premature, but an area ripe for further research.
Case Study: Biodistance Analysis Using Geometric Morphometrics
An example of using landmark coordinates from crania to investigate shape variation
among groups for the purposes of biodistance analysis is drawn from the dataset collected
