Ribcage Morphology in Native South American Populations From Different Altitudes: Insights From a Global Comparative...

Area of Science:

• Human evolutionary biology
• Anthropometry
• High-altitude adaptation

Background:

• Altitude significantly influences human morphology, particularly in cold and hypoxic highland environments.
• Previous research on Andean highlanders' ribcages relied on limited skeletal data and non-South American comparisons.
• Understanding ribcage variation is crucial for comprehending human adaptation to diverse environments.

Purpose of the Study:

• To investigate the 3D ribcage configuration of native South American populations.
• To analyze ribcage variation in relation to altitude and global populations.
• To clarify the adaptive significance of ribcage morphology in high-altitude dwellers.

Main Methods:

• 3D geometric morphometrics applied to 37 South American adult ribcages (17 highlanders, 20 lowlanders).
• Shape variation analyzed using Procrustes MANOVA and Principal Component Analysis (PCA).
• Centroid size used for size difference assessment, with comparisons to 92 worldwide lowlanders.

Main Results:

• South American highlanders and lowlanders display similar ribcage shapes, both deeper than worldwide lowlanders.
• No significant differences in absolute ribcage size were found between South American highlanders and lowlanders.
• Pronounced sexual dimorphism observed: males possess wider and larger ribcages than females.

Conclusions:

• Deep ribcage in South Americans may be a population-specific trait advantageous for high-altitude adaptation.
• South American highlanders may have larger relative ribcage size compared to their body size.
• Larger male ribcages suggest greater respiratory capacity and metabolic demands in males.