Date of Award
Bachelor of Arts (BA)
Dr. Frank L'Engle Williams
There is variation in Neandertal permanent dentition in both the size and shape of first molars. Ecogeography as well as chronology would be expected to account for at least some of the variation observed. Occlusal outlines of maxillary and mandibular first molar casts from European Neandertals, (Spy 1, Scladina 4A-4, Engis 2, l’Hortus 2, 4, 5, and 8, La Quina H5, Malarnaud 1) were generated through photostereomicroscopy and non-landmark smooth tracing methods, and occlusal areas, buccolingual breadths and mesiolingual lengths were measured by calibrated Motic 3.0MP microscope cameras. Principal component (PC) scores of elliptical Fourier harmonic descriptors were calculated using SHAPE v1.3, yielding a total of 76 and 67 PC scores for mandibular and maxillary data respectively.
Of the maxillary outlines analyzed, a strong correlation exists between PC1 (58.4% of variance) and occlusal area, explaining size influence. On PC1, the smallest (Engis 2), is followed by Scladina 4A-A, Hortus 8, La Quina 5 and Spy 1. On PC2 (23% of variance), Scladina 4A-A is an outlier. On PC3 (12.6%), Hortus 8 is separated from the others whereas Scladina 4A-A is difficult to classify. PC4 accounts for 5.8% of the variance and separates Spy 1 from La Quina 5. Spy 1 appears as distinct on PC1, PC3, and PC4 while Scladina 4A-A is relatively distinct on all axes. In a cluster analysis of PC scores Spy 1 and La Quina 5 are linked by the shortest distance and joined secondarily to Hortus 8, whereas Scladina 4A-A and Engis 2 are relatively distinct from the others.
Mandibular results indicate that Malarnaud is distinct on PC1 (40% of variance) and again on PC2 (27%), while La Quina 5 appears as slightly distinct on PC3 (14%), though grouped with Engis 2, while Hortus 2 and 4 group together this axis as well as PC1. PC4 (12%) again separates Malarnaud, and presents Hortus 5 as an outlier.
Overall, chronology correlates better than geography to the variance observed in occlusal first molar shape in these European Neandertals, with some inconsistencies most likely due to individual biological variability. This study demonstrates a new method to compute the elliptical Fourier descriptors of molar occlusal outlines, and applies these to explain variation in these Neandertals with respect to ecogeographic and chronological situation.
Anderson, William and Williams, Frank L., "From Scladina to Spy—A Morphometric Comparison of European Neandertal First Molar Occlusal Outlines using Elliptical Fourier Function Analysis." Thesis, Georgia State University, 2017.