The Use of Elliptical Fourier Analysis on Orbit Shape in Human Skeletal Remains

摘要

Human orbit shape has been previously analyzed with a few non-specific landmarks or with subjective shape descriptions. This study uses elliptical Fourier analysis, a landmark-free method of measurement, to quantify the entire shape of the orbit and test the influence of sex, age, ancestry, and geographic location on orbit shape. Digital photographs were taken of 162 individuals of known sex, age and ancestry from the skeletal collections in Knoxville, Tennessee and Pretoria, South Africa. Orbit contours were traced from the photos and then analyzed in the elliptical Fourier program "SHAPE v. 1.3". Principal component (PC) values from SHAPE were analyzed for significant contributing variables using an ANCOVA. In the full sample, PCs 1, 2, 4, and 5 were affected by at least one of the independent variables. Of these, geographical location figured prominently in 3 of the PCs. This underscores the importance of considering environmental effects over genetic ancestral affinities when analyzing human variation. Sex and the interaction between ancestry and continent of origin also significantly affected orbit shape. Although two PCs show some similarities to established descriptors of orbit shape, other components reveal more shape variation than have been previously prescribed. The corners of the orbits, features that are not captured in many current metric analyses, appear to play a significant role in shape variation. The technique used for this study proved to be effective in detecting significant contributing variables influencing human orbit shape. The study focused on descriptive analyses, but the quantitative data allows for the formulation of discriminant functions. These should not be hastily constructed as other variables associated with orbit shape remain unexplained.