Clavicular evidence for continued arboreality in Australopithecus afarensis.

Area of Science:

• Paleoanthropology
• Primate Anatomy
• Evolutionary Biology

Background:

• Hominin evolution is characterized by bipedalism, but the extent of arboreal behaviors during this transition remains debated.
• Australopithecus skeletons show a mosaic of traits, with lower limbs indicating bipedalism and upper limbs retaining ape-like arboreal features.

Purpose of the Study:

• To investigate the locomotor habits of Australopithecus afarensis by analyzing clavicular morphology.
• To explore functional signals in hominin clavicles using advanced imaging and geometric techniques.

Main Methods:

• Description of juvenile and adult Australopithecus afarensis clavicles.
• Application of geometric morphometrics and cortical cross-sectional geometry.
• Comparison of fossil clavicular morphology with extant apes (Pan and Homo).

Main Results:

• External clavicular shape in Australopithecus overlaps significantly with chimpanzees (Pan), challenging distinct human morphology.
• Internal cortical bone geometry shows plasticity and functional signals relevant to locomotor adaptations.
• Similarities in internal clavicular geometry between Australopithecus and modern apes suggest ongoing arboreal behaviors, including climbing and suspension.

Conclusions:

• Internal bone structure provides crucial functional insights often missed by external morphology alone.
• Australopithecus afarensis likely retained significant arboreal behaviors throughout life.
• Oversimplified taxonomic assignments based solely on external shape should be avoided in understanding hominin locomotor evolution.