1Interdepartmental Doctoral Program in Anthropological Sciences, Stony Brook University, 2Department of Anatomical Sciences, Stony Brook University School of Medicine, 3Department of Basic Medical Sciences, University of Arizona College of Medicine
March 27, 2015 11:45, Grand Ballroom A/B
Fossil hominin studies have used foot and ankle joint morphology to assess the prevalence of arboreal climbing in early hominins. Typically, these studies compare fossil hominin joint morphology to that of great apes, which are known to climb trees frequently in the wild. However, the actual mechanics of great ape ankle and midfoot joints during climbing are still poorly understood. To address this gap, we measured the motion of these joints in chimpanzees during vertical climbing, and compared it to motion measured during terrestrial quadrupedalism.
We collected kinematic data from two male chimpanzees (Pan troglodytes) (7.4±0.1 yrs; 38.6±3.4 kg) using a four-camera motion capture system (ProCapture, Xcitex Inc.). We used a seventeen-point leg and foot marker set to measure three-dimensional motion at the ankle and midfoot joints. Subjects were recorded climbing a 15cm diameter tree trunk and walking quadrupedally on a flat runway.
Our results indicate that chimpanzees dorsiflex their talocrural joints slightly more during climbing than during terrestrial quadrupedalism. However, the actual difference is small enough to suggest to us that the high dorsiflexion range of the chimpanzee ankle may not be an adaptation for climbing. We also found that chimpanzees adopt highly inverted subtalar and transverse tarsal joints during climbing, suggesting that these joints may be better indicators of climbing proficiency than the talocrural joint. Finally, chimpanzees exhibit relatively high dorsiflexion angles at their tarsometatarsal joints during climbing, particularly on the medial side of the foot, suggesting that heightened mobility in this region may represent a climbing adaptation.
Supported by NSF BCS-0935321, the Leakey Foundation, and the Wenner-Gren Foundation.