Sexual dimorphism in the human pelvis: testing a new hypothesis

Area of Science:

• Anthropology
• Human Anatomy
• Evolutionary Biology

Background:

• Sexual dimorphism in the human pelvis is debated regarding its obstetric significance.
• Previous studies have not definitively linked specific pelvic dimensions to parturition challenges.

Purpose of the Study:

• To investigate the relationship between human pelvic sexual dimorphism and parturition.
• To identify specific pelvic dimensions that exhibit significant sexual dimorphism and their obstetric implications.

Main Methods:

• Analysis of a large sample of complete human skeletons from the Coimbra Identified Skeletal Collection.
• Measurement of key dimensions of the true pelvis (birth canal), including inlet, midplane, and outlet diameters.

Main Results:

• Significant sexual dimorphism was observed in pelvic dimensions related to the birth canal.
• Specifically, anteroposterior diameter of the inlet, transverse diameter of the bispinous midplane, and transverse diameter of the outlet were notably larger in females.
• These dimensions are associated with biparietal deformation, a risk factor for neonatal mortality.

Conclusions:

• Human pelvic sexual dimorphism reflects differential selection pressures on males and females.
• The observed dimorphism has direct implications for the biomechanics of human parturition and neonatal outcomes.
• Findings provide a basis for further research into the evolution of modern human birth patterns.