Foot use during vertical climbing in chimpanzees (Pan troglodytes)

Area of Science:

• Paleoanthropology
• Primate Locomotion
• Functional Morphology

Background:

• Upright bipedalism is key in hominin evolution, but early hominin locomotion remains debated.
• Foot structure is crucial for understanding locomotion, with new fossil discoveries highlighting early human bipedalism's complexity.
• Understanding load distribution in extant apes is vital for interpreting fossil hominin foot adaptations.

Purpose of the Study:

• To analyze plantar pressure distribution in chimpanzees during vertical climbing.
• To provide functional data linking foot bone features to load distribution in the forefoot.
• To inform debates on early hominin locomotion and foot evolution.

Main Methods:

• Plantar pressure distribution was measured in chimpanzees climbing a vertical support.
• Analysis focused on load distribution across the forefoot during the climbing stance phase.
• Data were compared to existing knowledge of chimpanzee knuckle-walking and horizontal locomotion.

Main Results:

• Chimpanzees exhibit disproportionate loading of the medial metatarsals and first toe during vertical climbing.
• Peak pressures were highest on these elements at the end of the climbing stance phase.
• Forefoot toe pressures during climbing significantly exceed those during knuckle-walking or horizontal pole movement.

Conclusions:

• The study provides the first analysis of forefoot plantar pressure in chimpanzees during vertical climbing.
• Disproportionate loading on the first toe and medial metatarsals during climbing supports functional links to specific foot morphologies.
• These findings offer insights into the evolution of early hominin foot structure and locomotion, particularly adaptations for climbing.