From Grasping to Grooming to Gossip: Innovative Use of Chimpanzee Signals in Novel Environments Supports Both Vocal and Gestural Theories of Language Origins

Abstract

The unique challenges posed by ecologically novel situations can illuminate the limits of flexibility in animal signalling systems. Here we describe the innovative application of species-typical calls by chimpanzees exposed to the novel circumstances in which the animals are dependent upon others to act on the world for them, what we have previously termed "the Referential Problem Space". When chimpanzees are put into the Referential Problem Space, they display attention-getting calls and other auditory signals, and they tailor these signals to the state of attention of the receiver. Here we report that the kinds of calls that chimpanzees use in these evolutionarily novel circumstances are, generally, amplified versions of the same calls that they display in grooming contexts. Thus, this class of auditory signals, used in affiliative, grooming contexts, is chosen overwhelmingly by chimpanzees for application towards novel ends. This is consistent with Dunbar's (Grooming, gossip and the evolution of language. Faber and Faber, London, 1996) hypothesis that early humans substituted auditory contact for manual grooming as group sizes exceeded ca. 150 people. Moreover, these calls are primarily produced by supralaryngeal modulation of the airstream. This is consistent with Corballis's (From hand to mouth: The origins of language. Princeton University Press, Princeton, 2002) communication in humans moved from the hands to the mouth and then into the larynx. In contemporary chimpanzees, we find intentional modulation of calls focused at the fronts of their oral cavities, for most grooming calls.

Genetic Factors and Orofacial Motor Learning Selectively Influence Variability in Central Sulcus Morphology in Chimpanzees (Pan troglodytes)

“…Studies have demonstrated that some chimpanzees and other great apes voluntarily produce several classes of novel sounds to capture the attention of an otherwise inattentive audience (Theall and Povinelli, 1999;Liebal et al, 2004;Poss et al, 2006;Cartmill and Byrne, 2007;Leavens et al, 2008;Gentry et al, 2015). Experimental evidence has shown that the use of AG sounds is under voluntary control Hopkins et al, 2011), often occurs in conjunction with manual gestures (Hopkins and Cantero, 2003) and grooming (Leavens et al, 2014;Fedurek et al, 2015;Watts, 2016), is lateralized to the left hemisphere (Losin et al, 2008;Wallez et al, 2012), and is socially learned (Taglialatela et al, 2012). For instance, systematic investigations of the production of AG sounds in 279 chimpanzees from two different populations found that 52% and 46% of the chimpanzees within each sample reliably produce some type of AG sound, respectively (Hopkins et al, 2010;Taglialatela et al, 2012).…”

Pointing in the right direction. A discussion of The evolution of social communication in primates, eds. M. Pina and N. Gontier

“…The long-running debate about the nature of proto-language in our hominid ancestors is addressed in the chapters by Zlatev (2014), See (2014) and Leavens et al (2014), who offer a synthetic solution to the older gestural-versus-vocal origin of language debates by embracing a multimodal approach to the evolution of language. By claiming that communication has, from the very beginning, combined both gestures and vocalizations, they avoid "the greatest unsolved problem for gestural protolanguage theories", as Fitch (2010: 448) puts it: the problem of how gestural protolanguage transitioned into vocal language.…”

“…According to Zlatev (2014: 176), speech is a more economic modality to use in bigger groups (for counterarguments see Fitch 2010: 445) and speech is considered to be more symbolic and arbitrary, therefore better suited to "differentiate more clearly between an extensive set of concepts, even when their referents are visually similar." To explain how speech co-evolved with manual signals and eventually became the predominant modality, Leavens et al (2014) interestingly merge Dunbar's from grooming to gossip approach (1996) and Corballis's from hand to mouth approach (2002). According to Corballis, the brains of hominids were prepared for speech production through the long period of controlling intentional manual gestures by the left hemisphere (grooming is usually performed by the right hand).…”

“…Finally, because there is voluntary control over both intentionally-produced gestures as well as attention-getting calls, there is a factor of choice. Indeed, under experimental conditions, chimpanzees sometimes alternate between vocal and gestural signals to obtain a certain response when it is delayed by experimenters (Leavens et al, 2014).…”

“…It contains texts on the bodily mimesis origins of speech Pointing in the right direction... (Zlatev 2014), and multimodal accounts on language evolution (See 2014;Leavens, Taglialatela and Hopkins 2014).…”