Primate communication
Field primatologists can give useful insights into great ape communication in the wild.[31] An important[according to whom?] finding is that nonhuman primates, including the other great apes, produce calls that are graded, as opposed to categorically differentiated, with listeners striving to evaluate subtle gradations in signallers’ emotional and bodily states. Nonhuman apes seemingly find it extremely difficult to produce vocalisations in the absence of the corresponding emotional states.[42] In captivity, nonhuman apes have been taught rudimentary forms of sign language or have been persuaded to use lexigrams—symbols that do not graphically resemble the corresponding words—on computer keyboards. Some nonhuman apes, such as Kanzi, have been able to learn and use hundreds of lexigrams.[154][155]
The Broca’s and Wernicke’s areas in the primate brain are responsible for controlling the muscles of the face, tongue, mouth, and larynx, as well as recognizing sounds. Primates are known to make “vocal calls”, and these calls are generated by circuits in the brainstem and limbic system.[156]
In the wild, the communication of vervet monkeys has been the most extensively studied.[153] They are known to make up to ten different vocalizations. Many of these are used to warn other members of the group about approaching predators. They include a “leopard call”, a “snake call”, and an “eagle call”.[157] Each call triggers a different defensive strategy in the monkeys who hear the call and scientists were able to elicit predictable responses from the monkeys using loudspeakers and prerecorded sounds. Other vocalisations may be used for identification. If an infant monkey calls, its mother turns toward it, but other vervet mothers turn instead toward that infant’s mother to see what she will do.[158][159]
Similarly, researchers have demonstrated that chimpanzees (in captivity) use different “words” in reference to different foods. They recorded vocalisations that chimps made in reference, for example, to grapes, and then other chimps pointed at pictures of grapes when they heard the recorded sound.[160][161]
Ardipithecus ramidus[edit]
A study published in HOMO: Journal of Comparative Human Biology in 2017 claims that Ardipithecus ramidus, a hominin dated at approximately 4.5Ma, shows the first evidence of an anatomical shift in the hominin lineage suggestive of increased vocal capability.[162] This study compared the skull of A. ramidus with 29 chimpanzee skulls of different ages and found that in numerous features A. ramidus clustered with the infant and juvenile measures as opposed to the adult measures. Significantly,[according to whom?] such affinity with the shape dimensions of infant and juvenile chimpanzee skull architecture, it was argued, may have resulted in greater vocal capability. This assertion was based on the notion that the chimpanzee vocal tract ratios that prevent speech are a result of growth factors associated with puberty—growth factors absent in A. ramidus ontogeny. A. ramidus was also found to have a degree of cervical lordosis more conducive to vocal modulation when compared with chimpanzees as well as cranial base architecture suggestive of increased vocal capability.
What was significant in this study[according to whom?] was the observation that the changes in skull architecture that correlate with reduced aggression are the same changes necessary for the evolution of early hominin vocal ability. In integrating data on anatomical correlates of primate mating and social systems with studies of skull and vocal tract architecture that facilitate speech production, the authors argue that paleoanthropologists to date[when?] have failed to understand the important relationship between early hominin social evolution and language capacity.
While the skull of A. ramidus, according to the authors, lacks the anatomical impediments to speech evident in chimpanzees, it is unclear what the vocal capabilities of this early hominin were. While they suggest A. ramidus—based on similar vocal tract ratios—may have had vocal capabilities equivalent to a modern human infant or very young child, they concede this is obviously a debatable and speculative hypothesis. However, they do claim that changes in skull architecture through processes of social selection were a necessary prerequisite for language evolution. As they write:
We propose that as a result of paedomorphic morphogenesis of the cranial base and craniofacial morphology Ar. ramidus would have not been limited in terms of the mechanical components of speech production as chimpanzees and bonobos are. It is possible that Ar. ramidus had vocal capability approximating that of chimpanzees and bonobos, with its idiosyncratic skull morphology not resulting in any significant advances in speech capability. In this sense the anatomical features analysed in this essay would have been exapted in later more voluble species of hominin. However, given the selective advantages of pro-social vocal synchrony, we suggest the species would have developed significantly more complex vocal abilities than chimpanzees and bonobos.[162]
Early Homo[edit]
Anatomically, some scholars believe that features of bipedalism developed in the australopithecines around 3.5 million years ago. Around this time, these structural developments within the skull led to a more prominently L-shaped vocal tract.[163][page needed] In order to generate the sounds modern homo sapiens are capable of making, such as vowels, it is vital that Early Homo populations must have a specifically shaped voice track and a lower sitting larynx.[164] Opposing research previously suggested that Neanderthals were physically incapable of creating the full range of vocals seen in modern humans due to the differences in larynx placement. Establishing distinct larynx positions through fossil remains of Homo sapiens and Neanderthals would support this theory; however, modern research has revealed that the hyoid bone was indistinguishable from the two populations. Though research has shown a lower sitting larynx is important to producing speech, another theory states it may not be as important as once thought.[165] Cataldo, Migliano, & Vinicius (2018) stated that speech may have emerged due to an increase in trade and communication between different groups. Another view by Cataldo states that speech was evolved to enable tool-making by the Neanderthals.[166]
Archaic Homo sapiens[edit]
Further information: Archaic humans
Steven Mithen proposed the term Hmmmmm for the pre-linguistic system of communication posited to have been used by archaic Homo, beginning with Homo ergaster and reaching the highest sophistication in the Middle Pleistocene with Homo heidelbergensis and Homo neanderthalensis. Hmmmmm is an acronym for holistic (non-compositional), manipulative (utterances are commands or suggestions, not descriptive statements), multi-modal (acoustic as well as gestural and facial), musical, and mimetic.[167]
Homo heidelbergensis[edit]
See also: Homo heidelbergensis: Language
Homo heidelbergensis was a close relative (most probably a migratory descendant) of Homo ergaster. Some researchers believe this species to be the first hominin to make controlled vocalisations, possibly mimicking animal vocalisations,[167] and that as Homo heidelbergensis developed more sophisticated culture, proceeded from this point and possibly developed an early form of symbolic language.
Homo neanderthalensis[edit]
See also: Neanderthal behavior: Language
The discovery in 1989 of the (Neanderthal) Kebara 2 hyoid bone suggests that Neanderthals may have been anatomically capable of producing sounds similar to modern humans.[168][169] The hypoglossal nerve, which passes through the hypoglossal canal, controls the movements of the tongue, which may have enabled voicing for size exaggeration (see size exaggeration hypothesis below) or may reflect speech abilities.[26][170][171][172][173][174]
However, although Neanderthals may have been anatomically able to speak, Richard G. Klein in 2004 doubted that they possessed a fully modern language. He largely bases his doubts on the fossil record of archaic humans and their stone tool kit. Bart de Boer in 2017 acknowledges this ambiguity of a universally accepted Neanderthal vocal tract; however, he notes the similarities in the thoracic vertebral canal, potential air sacs, and hyoid bones between modern humans and Neanderthals to suggest the presence of complex speech.[175] For two million years following the emergence of Homo habilis, the stone tool technology of hominins changed very little. Klein, who has worked extensively on ancient stone tools, describes the crude stone tool kit of archaic humans as impossible to break down into categories based on their function, and reports that Neanderthals seem to have had little concern for the final aesthetic form of their tools. Klein argues that the Neanderthal brain may have not reached the level of complexity required for modern speech, even if the physical apparatus for speech production was well-developed.[176][177] The issue of the Neanderthal’s level of cultural and technological sophistication remains a controversial one.[citation needed]
Based on computer simulations used to evaluate that evolution of language that resulted in showing three stages in the evolution of syntax, Neanderthals are thought to have been in stage 2, showing they had something more evolved than proto-language but not quite as complex as the language of modern humans.[178]
Some researchers, applying auditory bioengineering models to computerised tomography scans of Neanderthal skulls, have asserted that Neanderthals had auditory capacity very similar to that of anatomically modern humans.[179] These researchers claim that this finding implies that “Neanderthals evolved the auditory capacities to support a vocal communication system as efficient as modern human speech.”[179]
Homo sapiens[edit]
See also: Anatomically modern humans and Behavioral modernity
Anatomically modern humans begin to appear in the fossil record in Ethiopia some 200,000 years ago.[180] Although there is still much debate as to whether behavioural modernity emerged in Africa at around the same time, a growing number of archaeologists nowadays[when?] invoke the southern African Middle Stone Age use of red ochre pigments—for example at Blombos Cave—as evidence that modern anatomy and behaviour co-evolved.[181] These archaeologists argue strongly that if modern humans at this early stage were using red ochre pigments for ritual and symbolic purposes, they probably had symbolic language as well.[28]
According to the recent African origins hypothesis, from around 60,000 – 50,000 years ago[182] a group of humans left Africa and began migrating to occupy the rest of the world, carrying language and symbolic culture with them.[183]