Diagnostic differences in mandibular P4 shape between Neandertals and anatomically modern humans

Area of Science:

• Paleoanthropology
• Dental Morphology
• Evolutionary Biology

Background:

• Qualitative assessments previously suggested significant P(4) crown shape differences between Neandertals and anatomically modern humans.
• Previous studies relied on subjective shape assessments, lacking quantitative data for robust taxonomic classification.

Purpose of the Study:

• To quantitatively analyze P(4) crown shape differences between Neandertals and anatomically modern humans using elliptical Fourier analysis.
• To determine the utility of P(4) shape for taxonomic classification and phylogenetic analysis of hominin species.
• To investigate the evolutionary implications of P(4) asymmetry in Neandertals.

Main Methods:

• Elliptical Fourier analysis was employed to quantify P(4) crown shape variations.
• Statistical analyses, including randomization tests, principal component analysis, and discriminant function analysis, were used to assess shape differences and classification accuracy.
• Mean shapes of Neandertal and anatomically modern human P(4) crowns were compared.

Main Results:

• A significant shape difference was confirmed, with Neandertals exhibiting a truncated mesiolingual portion of the P(4), resulting in distinct asymmetry.
• Discriminant function analysis showed that while overall classification was 86.4%, accuracy was higher for anatomically modern humans (98.1%) than Neandertals (65%).
• Neandertal P(4) crowns were found to be narrower on the lingual portion compared to anatomically modern humans.

Conclusions:

• P(4) crown asymmetry is a significant dental morphological character that distinguishes Neandertals from anatomically modern humans.
• Symmetry appears to be the primitive state, with P(4) asymmetry likely being a derived trait in Neandertals.
• The quantitative analysis of P(4) shape provides valuable data for understanding hominin evolution and classification.