The role of genetic drift in shaping modern human cranial evolution: a test using microevolutionary modeling

Area of Science:

• Human evolution
• Paleoanthropology
• Population genetics

Background:

• Understanding microevolutionary processes shaping modern human cranial variation is incomplete.
• Cranial variation patterns are key to reconstructing human evolutionary history.

Purpose of the Study:

• To compare variance/covariance (V/CV) structure of cranial modules across global human populations.
• To investigate the influence of microevolutionary processes on modern human skull morphology.

Main Methods:

• Applied a microevolutionary framework to analyze V/CV structure.
• Compared cranial modules including basicranium, temporal bone, and face across a worldwide sample.
• Assessed correlations between morphological similarity and geographic distance.

Main Results:

• V/CV patterns in basicranium, temporal bone, and face align with neutral evolution hypotheses.
• Mandibular morphology exhibited a pattern inconsistent with neutral evolution.
• Geographic distance significantly correlated with similarity in facial, temporal bone, and mandibular morphology, though variance remains unexplained.

Conclusions:

• Findings suggest signatures of genetic drift, gene flow, and migration in human cranial variation.
• Mandibular morphology may reflect distinct selective pressures or evolutionary mechanisms.
• Provides a foundation for inferring selective pressures faced by early human migrants.