Hand and forearm musculature of the brachiating apes: with particular reference to the structure and function of the Orang Utan (Pongo pygmaeus). Implications for hominid evolution.

Abstract

Great ape musculature is frequently referred to in relation to theories of hominid evolution, particularly the evolution of upright bipedalism. For these theories to have validity it is important for ape musculature to be well documented. This is currently not the case. Information, especially on orang utans, is scarce and from dissection of only a few individuals. In this study three adult, one infant and two foetal orang utans, and an assortment of hylobatid cadavers were studied. The muscles of the three adult and one infant orang utans were measured and origins and insertions recorded. From this the function of the muscles and possible relations with locomotory and manipulatory activities were discussed. In conclusion brachiating apes were found to have forearm musculature specialised for locomotion and hand musculature specialised for manipulation. This information can be used in relation to theories regarding the development of precision manipulation and upright bipedalism in hominids.