Metacarpal trabecular architecture variation in the chimpanzee (Pan troglodytes): Evidence for locomotion and tool-use?
Trabecular architecture was assessed by 3D micro-computed tomography from spherical volumes of interest located within the head and base of metacarpals (MC) 1, 2, and 5 from n = 19 adult common chimpanzees. Two subspecies, West African Pan troglodytes verus from the Taï Forest, Côte d'Ivoire (n = 12) and Central African P. t. troglodytes from Cameroon (n = 7), were studied. For the combined sample, the metacarpal head is distinguished by greater bone volume fraction across all metacarpals, though the MC 1 is distinctive in having thicker, more plate-like trabeculae. The architecture in the MC 2 and MC 5 can be related to strains associated with terrestrial knuckle-walking. In particular, the relatively robust MC 5 head architecture may result from functional loading incurred during braking and use of a palm-in hand posture. Examining differences between samples, we found that the Cameroon chimpanzees possess a more robust architecture across all metacarpals in the form of greater bone volume fraction, higher connectivity, and somewhat more plate-like structure. These differences are not explicable in terms of population distinctions in body size or daily travel distance, but possibly reflect a combination of more terrestrial knuckle-walking in the Cameroon sample and more diverse hand postures and precision handling required of nut-cracking in West African chimpanzees.
Lazenby
Richard A
RA
University of Northern British Columbia, Prince George, BC, Canada V2N4Z9. lazenby@unbc.ca
Skinner
Matthew M
MM
Hublin
Jean-Jacques
JJ
Boesch
Christophe
C
D000704:Analysis of Variance; D000818:Animals; D005260:Female; D008124:Locomotion / Q000502:physiology*; D008297:Male; D050279:Metacarpal Bones / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000502:physiology*; D009754:Nuts; D002679:Pan troglodytes / Q000033:anatomy & histology* / Q000502:physiology*; D018709:Statistics, Nonparametric; D053001:Tool Use Behavior / Q000502:physiology*; D055114:X-Ray Microtomography