................................ Chapter 10 ................................ ................................ The Special Demands of Great Ape ................................ ................................ chapter Locomotion and Posture ................................ ................................ Kevin D. HUNT ................................ Department of Anthropology, Indiana University, ................................ Student Building 130, 701 E. Kirkwood Avenue, ................................ Bloomington, IN 47405–7100 March 2003 ................................ ................................ A-Head 1 Introduction ................................ 2 Amidst the welter of competencies that could be labeled “intelligence”, the ................................ 3 great apes repeatedly demonstrate numerous high-level abilities that ................................ 4 distinguish them from other mammals and ally them with humans (Griffin c10rfa039................................ c10rfa034 5 1982; Parker & Gibson 1990; Russon, Parker & Bard 1996; Suddendorf & c10rfa083................................ c10rfa092 6 Whiten 2001). Self-concept is argued to be among this set of distinctive ................................ ................................ Word count: 6912 (text), (reference) 2688 ................................ XML Typescript c Cambridge University Press – Generated by TechBooks. Ape Locomotion and Posture Page 630 of 1365 1 abilities. It is often viewed as an integral aspect of advanced intelligence, ................................ 2 one that some have argued allows great apes to have a theory of mind ................................ c10rfa041 3 (Heyes 1998 and references therein). Among the abilities that co-occur ................................ 4 with it in humans are symbolic play, simple altruism, reciprocal ................................ 5 relationships, a concept of planning, and pleasure in completion of ................................ c10rfa074 6 complex tasks (Povinelli & Cant 1995). ................................ 7 Until recently, the demands of locomotion and posture, together ................................ c10rfa075 8 referred to as positional behavior (Prost 1965), were not explicitly ................................ 9 considered to correlate with any aspect of primate intelligence or its ................................ 10 evolution, self-concept included. Primate intelligence is most often ................................ 11 hypothesized to have evolved either for negotiating complex social ................................ 12 problems, or for mapping and resolving complicated foraging challenges ................................ 13 (for an overview, see Russon this volume a). Chevalier-Skolnikoff, ................................ c10rfa016 14 Galdikas and Skolnikoff (1982: 650) suggested instead that, at least for ................................ 15 orangutans, locomotor demands were “the single major function for which ................................ c10rfa074 16 the advanced cognitive abilities ...evolved.” Povinelli and Cant (1995) ................................ 17 subsequently refined and expanded this hypothesis, asserting that ................................ 18 self-concept in orangutans evolved to enable these large-bodied apes to ................................ 19 negotiate thin, compliant (i.e., flexible) branches during suspensory ................................ 20 locomotor bouts, particularly when crossing gaps in the canopy. They ................................ XML Typescript c Cambridge University Press – Generated by TechBooks. The Evolution of Thought Page 631 of 1365 1 hypothesized that the unpredictable response of compliant weight-bearing ................................ 2 structures when weight is transferred onto them, the need for several such ................................ 3 structures to support the weight of a single individual, and the erratic ................................ 4 orientation of supports together require that large primates such as great ................................ 5 apes have an “ability to engage in a type of mental experimentation or ................................ 6 simulation in which one is able to plan actions and predict their likely ................................ c10rfa074 7 consequence before acting” (Povinelli & Cant 1995: 409). In order to move ................................ 8 safely in the forest canopy, orangutans and perhaps other great apes must ................................ 9 be able to step outside themselves and imagine how their body and its ................................ 10 movements will affect fragile, easily deformable branches and twigs. I will ................................ 11 refer to these argument as the “Povinelli and Cant hypothesis,” cognizant ................................ 12 of Chevalier-Skolnikoff et al.’s contribution. ................................ 13 This hypothesis is consistent with evidence that only massive ................................ 14 primates, the great apes, have a concept of self. Evidence rests heavily on ................................ 15 one measure, mirror self-recognition (MSR), which is often taken as ................................ c10rfa030 c10rfa031 16 particularly informative about self-concept. Gallup (1970, 1982, 1991) ................................ c10rfa032 17 forcefully argued that MSR is found only in species that possess a ................................ c10rfa066 18 self-concept, and Parker (1996) contended it is displayed only in species ................................ 19 that also display high-level imitation. Chimpanzees and orangutans ................................ 20 consistently recognize themselves in mirrors, as do a few gorillas, whereas ................................ XML Typescript c Cambridge University Press – Generated by TechBooks. Ape Locomotion and Posture Page 632 of 1365 c10rfa030 c10rfa057 1 other nonhuman primates do not (Gallup 1970; Lethmate & Ducker 1973; ................................ c10rfa061 c10rfa064 2 Miles 1994; Nicholson & Gould 1995; Patterson 1984; Patterson & Cohn ................................ c10rfa070 c10rfa069 c10rfa091 3 1994; Suarez & Gallup 1981; Swartz et al. 1999; see reviews by Gallup ................................ c10rfa097 1 c10rfa032 4 1991; Inoue-Nakamura 1997) . Although other capacities that co-occur ................................ c10rfa050 5 with self concept such as symbolic play, simple altruism, reciprocal ................................ 6 relationships, a concept of planning, and pleasure in completion of ................................ 7 complex tasks are not a cleanly identifiable in any species, narratives of the ................................ 8 daily lives of great apes in captivity and in the wild convince me they have ................................ 9 these capacities. ................................ 10 From the positional side, this hypothesis has not been systematically ................................ 11 evaluated. This chapter attempts to craft informed estimates of locomotor ................................ 12 and postural frequencies for each of the apes in order to place positional ................................ 13 behavior in the context of Povinelli and Cant hypothesis, as well as other ................................ 14 prominent hypotheses on the evolution of great ape intelligence, namely ................................ 15 foraging-related ecological pressures and social pressures. ................................ ................................ A-Head 16 Background ................................ 17 The connection between primate positional behavior and self-concept or ................................ 18 other higher cognitive capabilities receives prima facie support from ................................ 19 research on great apes – they are unusually suspensory. However, ................................ XML Typescript c Cambridge University Press – Generated by TechBooks. The Evolution of Thought Page 633 of 1365 1 quantitative studies of apes’ positional behavior are relatively recent and ................................ 2 the meaning of these data is still in contention. Perhaps one source of the ................................ 3 contention is that positional behavior theory has a long history, and thus a ................................ 4 deep timescale to add heft to opposing hypotheses. Currently, two distinct ................................ 5 positional modes (or categories–Iwill use modes here) are most often ................................ 6 argued to be responsible for ape anatomy: vertical climbing and ................................ 7 arm-hanging. The two modes have quite different demands relative to the ................................ 8 Povinelli and Cant hypothesis. ................................ 9 Early research on ape functional anatomy was grounded in anatomical ................................ 10 research, a field already well developed by the nineteenth century (Owen ................................ c10rfa065 c10rfa085 11 1835; Savage & Wyman 1847; Tyson 1699), rather than in ape positional ................................ c10rfa101 c10rfa055 12 behavior study, which began in earnest only in the 1960s. Keith’s (1891) ................................ 13 contention that brachiation was the behavior for which ape specializations ................................ 14 were evolved permeated early research on ape positional