Model for the examination of evolutionary trends in tooth development

Area of Science:

• Paleoanthropology
• Developmental Biology
• Dental Morphology

Background:

• Teeth exhibit complex growth patterns that are challenging to study non-destructively.
• The second deciduous molar (DM2) and first permanent molar (M1) offer a model for studying intra-individual growth variation due to morphological similarities.
• Computerized tomography (CT) scanning provides a non-invasive method for analyzing tooth development.

Purpose of the Study:

• To evaluate serial CT scanning as a method for assessing tooth development and comparing modern and fossil hominin teeth.
• To investigate growth differences between the dentine-enamel junction (DEJ) and outer enamel surface (OES) in DM2 and M1.
• To compare tooth development patterns in a recent archaeological sample with early Homo sapiens sapiens from Skhul I.

Main Methods:

• Serial CT scans were performed on 31 archaeological specimens.
• Intercusp distances at the DEJ and OES were measured using a form distance matrix to quantify form and size differences.
• Measurements from recent teeth were compared to those of DM2 and M1 from Skhul I.

Main Results:

• Form differences between DM2 and M1 were smaller at the DEJ than at the OES, indicating that differences increase during development.
• Increased intercusp distances from DEJ to OES reflect cusp angulation, not enamel thickness.
• Fossil teeth from Skhul I showed smaller form differences between DM2 and M1 compared to the recent sample, with M1 differing more from its fossil counterpart.

Conclusions:

• CT scanning is effective for non-destructive analysis of tooth development and inter-tooth variation.
• The growth patterns observed in Skhul I suggest potentially earlier crown completion in M1 compared to recent populations.
• Similarities between Skhul permanent and deciduous teeth and recent DM2 may indicate conserved developmental pathways.