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Within Arm’s Reach: Measuring Forearm Length to Assess Growth Patterns in Captive Bonobos and Chimpanzees

Behringer, Verena, Stevens, Jeroen M.G., Kivell, Tracy L., Neufuss, Johanna, Boesch, Christophe, Hohmann, Gottfried (2016) Within Arm’s Reach: Measuring Forearm Length to Assess Growth Patterns in Captive Bonobos and Chimpanzees. American Journal of Physical Anthropology, 161 (1). pp. 37-43. ISSN 0002-9483. E-ISSN 1096-8644. (doi:10.1002/ajpa.23004)

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http://dx.doi.org/10.1002/ajpa.23004

Abstract

Objectives: Bonobos and chimpanzees are known to differ in various morphological traits, a dichotomy that is sometimes used as an analogy for evolutionary splits during human evolution. The aim of our study was to measure the forearm length of immature and adult bonobos and adult chimpanzees to assess the extent of age–related changes of forearm length in bonobos and sex–dimorphism in bonobos and chimpanzees.

Materials and methods: As a proxy of somatic growth we measured forearm length of captive bonobos and chimpanzees ranging in age from 1 to 55 years. Measures were taken from subjects inserting their arms into a transparent Plexiglas® tube, a novel technique facilitating repeated measures of nonanesthetized apes in captivity.

Results:Measures from adult females (>12 years) showed that bonobos exceed chimpanzees in terms of forearm length and that sexual dimorphism in forearm length is pronounced in chimpanzees, but not in bonobos. Forearm length increased significantly with chronological age in bonobos. Validation tests revealed that the device generates useful data on morphometric dimensions.

Discussion: In most primates, sexual dimorphism in body size is male-biased and the differences in forearm length in chimpanzees follow this trend. Given that males of the two species did not differ in forearm length, the absence/presence of sexual dimorphism of this trait must be due to differences in somatic growth in females. Our novel method offers an alternative to obtain morphometric measures and facilitates longitudinal studies on somatic growth.

Item Type: Article
DOI/Identification number: 10.1002/ajpa.23004
Subjects: Q Science > QL Zoology
Q Science > QM Human anatomy
Divisions: Faculties > Social Sciences > School of Anthropology and Conservation > Biological Anthropology
Depositing User: Tracy Kivell
Date Deposited: 12 Aug 2016 13:19 UTC
Last Modified: 16 Aug 2019 07:35 UTC
Resource URI: https://kar.kent.ac.uk/id/eprint/56827 (The current URI for this page, for reference purposes)
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