Trabecular bone structure in the primate wrist.

Area of Science:

• Paleoanthropology
• Biomechanics
• Comparative Anatomy

Background:

• Trabecular bone responds to mechanical loading, offering insights into skeletal function and locomotion.
• Hand trabecular bone is particularly informative due to direct substrate contact during quadrupedal locomotion.

Purpose of the Study:

• Investigate wrist trabecular structure in haplorhine primates with varying locomotor behaviors and body sizes.
• Determine if trabecular parameters differ based on hand use and load, and if they scale with carpal size.

Main Methods:

• High-resolution microtomographic scans of the lunate, scaphoid, and capitate from 41 individuals across eight genera.
• Analyses of variance and principal component analyses to assess functional signals and allometric scaling.

Main Results:

• No clear functional signal was found in wrist trabecular structure across suspensory, quadrupedal, and bipedal primates.
• Homo sapiens showed lower relative bone volume (BV/TV) compared to other taxa.
• Wrist trabecular parameters scaled with size, following established allometric patterns.

Conclusions:

• Trabecular bone structure in primate wrists may not strongly reflect locomotor differences, with significant intra-group variation observed.
• Human wrist bone volume is unique, likely due to reduced reliance on hands for locomotion.
• Allometric scaling of wrist trabecular bone is consistent with broader mammalian skeletal patterns.