This paper synthesizes available communication research and proposes 15 nonverbal steps leading to the origin of gestural and vocal language in genus Homo. Each step worked its way into tissues of the human nervous system. In combination and in synergy, the steps enabled modern linguistic communication in Homo sapiens. The neuromuscular changes occasioned in each step--and their roles in gestured and spoken language--are outlined and explored.
Bioneurology; Gesture; Language origins; Nonverbal communication
* Speech and gesture are rooted in a shared caudal-hindbrain, upper-spinal-cord compartment.
* Intra-species communication serves a reproductive function, later co-opted by language.
* Nonverbal messaging set standards for later speech and gesture.
* Language builds upon early, preexisting systems of vertebrate communication.
* Language reflects the earlier systems' roles in self-assertion, species recognition, genetic reproduction, emotional expression, and attention to objects.
Nonverbal Steps to the Origin of Language
This paper approaches the origin of language from the seemingly paradoxical perspective of nonverbal communication. Nonverbal messaging preceded linguistic expression by three billion years. The former not only came before, but also established the patterns and standards of linguistic communication through gesture and by word of mouth. It is proposed below that human language--in both its vocal and gestural forms--was superimposed upon the older nonverbal medium of expression (to explore the latter form of communication, see Givens 2015). Today’s verbal communication reflects the earlier medium’s role in (1) self-assertion, (2) species recognition, (3) genetic reproduction, (4) emotional expression, and (5) attention to objects.
Medium of the molecule. Nonverbal communication originated some 3.5 billion years ago in unicellular organisms known as cyanobacteria (blue-green algae), early life forms that inhabited shallow-water communities called stromatolites. Voiceless, eyeless, unable to touch or hear, earth’s first residents communicated chemically through the medium of the molecule.
Chemical cues represent the first of 15 communicative steps that led to the origin of manually signed and spoken language in genus Homo. This article synthesizes research and outlines each of the adaptive stages that led to language--from the chemical messages of cyanobacteria to the sonorous vocalizations of human speech today.
Step 1 (3.5 billion years ago): Chemical Messages--“I am Here”
Summary. Before neurons or brains existed, it was established that organisms should communicate through messaging molecules about matters of reproductive function. Known as oligopeptides, such molecules were used for intercellular quorum sensing. In living bacteria (e.g., Escherichia coli), Niu and colleagues characterize quorum sensing as a form of sophisticated “linguistic”-like communication involved in bacterial reproduction (Niu et al. 2013). Today the oligopeptide neurotensin is found in human-brain circuits, including those of prefrontal cortex, Broca’s area, and parts of the limbic system (St-Gelais et al. 2006). The fundamental meaning of early chemical messages was about physical presence: “I am here.”
I am here. From the beginning of life, intra-species communication has served a reproductive function. In cyanobacteria, individual organisms emitted chemical signals to announce physical presence--saying, essentially, “I am here”--to fellow bacteria in the community. Emitted messaging molecules (e.g., acyl-homoserine lactones) were not addressed to any one bacterium in particular, but rather to bacteria in the stromatolite as a whole. Nor did individual bacteria respond back directly to any one sender. Instead, the entire group responded collectively to the census-like messages about population density through quorum sensing. Based on the overall volume of chemical “I am here” signals received, the stromatolite community--as an aggregate--enacted changes to its reproductive gene expression (Miller & Bassler 2001).
In cyanobacteria and other organisms, “I am here” messages are in keeping with the basic biology of species recognition. Recognition of one’s own species members serves a reproductive function, in that conspecifics must somehow recognize one another as potential reproductive partners (Ridley 2004).
Regarding human language, “I am here” is implicit today in every signed movement and spoken word. The linguistic sign--whether visible or auditory--is a token of physical presence. Established in early life forms, this most basic of self assertions may be considered a necessary, but not a sufficient, first step toward linguistic communication in Homo.
Step 2 (500 million years ago): Vertebrate Messages--“I am Here” (Advent of “I/Me”)
Summary. In chordates, circuits for vocal-laryngeal and pectoral-movement communication link in a caudal hindbrain, rh8-upper-spinal-cord compartment (Bass & Chagnaud 2013). The neurological linkage explains why hand gestures and vocalizations are intimately coupled in the evolution of tool making and speech. Among the earliest audiovisual messages was the aforementioned assertion of “I/me,” viz., that “I am here.”
Retaining chemical messages through scent glands, vertebrates added audiovisual signals to further announce physical presence. It was established early on in chordates that respiratory vocalization and forelimb movements should be key players in audiovisual communication. Beginning 500 million years ago, circuits for vocal and movement communication were linked in a specific compartment of the chordate nervous system. Then, as today, this compartmental linkage explains why vertebrates—from fish to reptiles to human beings—call attention to themselves through respiratory sounds (e.g., vocalizations) and pectoral-area limb movements (e.g., gestures).
From the gorilla’s (Gorilla gorilla) chest-beating, the catfish’s (Synodontis schoutedeni) pectoral-fin squeaks, the humpback whale’s (Megaptera novaeangliae) pectoral flipper-slaps, and the human being’s (Homo sapiens) hand-waving, all such signals are pectoral cues tendered to announce physical presence. All may be accompanied, variously, by laryngeal vocalizations, vocal roars, drumming sounds (produced by swim bladders), and “singing” (emitted from a whale’s respiratory system). All are messages designed to announce the fact of “me”—to say, “I am here.”
The word “I” is included in Swadesh’s (1971) intuited list of 100 universal vocabulary items. “I” words tend to be phonetically simple and monosyllabic, a testimony, perhaps, to their elementary origin. In African languages, for example, “I/me” is expressed variously by “me” (!Kung “mi”), “nee” (Hausa “ni”), and “tee” (Hottentot “ti”; Ruhlen 1994, p. 35). (Items in quotes are English pronunciations; items in parentheses are phonetic transcriptions.) In Native American languages, “I/my” is expressed variously by “no” (Resigaro “no”), “see” (Carrier “si”), and “neen” (Micmac “nin”; Ruhlen 1994, p. 52).
Like a cyanobacterium’s chemical expression of “me,” audiovisual advertisements-of-self subserve a reproductive function. In human courtship, “I am here” messages are a part of courting’s Attention Phase, the first of four stages in a progression leading to sexual contact (Givens 1978, 2005). Before speaking, unacquainted couples may call attention to themselves through attractive clothing and with smiles, conspicuous gestures, and loud laughter. In the first stage of courtship “I am here” is often expressed nonverbally and apart from words.
Regarding linguistic communication, audiovisual “I am here” messages are implicit today in both signed and spoken words. Such messages may be considered a necessary, but not a sufficient, second step toward language in Homo.
Step 3 (500 million years ago): Vertebrate Messages--“You are There” (Advent of “You”)
Summary. In service to species recognition and reproductive function, sensorimotor systems of the vertebrate brain respond to “I/me” assertions with messages recognizing “you,” viz., that “you are there.” Ancient “you” messages built a foundation for the back-and-forth, dialogic pattern of speech.
You. Coincidental with Step 2, vertebrate audiovisual communication added a two-way, interpersonal dimension to the one-way chemical signals of cyanobacteria. Vertebrate message receivers could recognize and respond in kind to a sender’s nonverbal Attention Phase cues. By responding to an “I am here” message, a recipient implicitly recognizes “you,” the sender, and the fact that “you are there.” Once again, a great deal of this early messaging served a reproductive function in courtship.
In short, my son, note her every action and movement. If you report to me faithfully all these things, I shall be able to make out the hidden secret of her heart and discover how she feels with regard to my love; for I may tell you, Sancho, if you do not know it already, that among lovers exterior signs of this sort are the most reliable couriers that there are, bringing news of what goes on inside the heart. --Miguel de Cervantes, Don Quixote (1605, p. 566)
The second stage in courtship communication has been called the Recognition Phase (Givens 1978, 2005). In this stage couples seek nonverbal responses to signs emitted in the preceding Attention Phase. A man’s initial bid for attention (“I am here") may be followed, for example, by a woman’s direct eye contact, responsive smile, and hair-preening gestures (Scheflen 1965). These and other nonverbal signs reveal a recipient’s unspoken acknowledgement that a sender’s message has been seen or heard. They proclaim, apart from words, that “you are there.” Recognition cues are the afferent (incoming) bodily signals received in response to a sender’s efferent (outgoing) Attention Phase cues.
Like the “I” word, “you” is included in Swadesh’s (1971) list of 100 basic vocabulary items. And indeed, the “you” expression may be a linguistic universal. Like “I,” “you” tends to be phonetically simple and monosyllabic. In African languages, for instance, “you” is expressed variously by “yeen” (Dinka “yin”), “kai” (Hausa “kai”), and “coo” (Mbundu “ku”; Ruhlen 1994, p. 35). In Native American languages, “you” may be expressed as “bee” (Arawak “bi”), “geel” (Micmac “gil”), and “nee” (Navaho “ni”; Ruhlen 1994, p. 52).
Nonhuman courtship proceeds upon wordless “you”-like messages. For example, in the hamlet fish (Hypoplectrus unicolor), a hermaphroditic “male’s” Attention Phase spawning sound--produced by pectoral-girdle muscle contractions and vibrating muscles attached to the swim bladder--may be recognized with fin-spreading and bodily-quivering signs returned by the hermaphroditic “female.” In diverse species of frogs (Rana sp.), a male’s mating call and inflated vocal sacs while calling may be recognized by a female’s submissively lowered-body. In the Puerto Rican dwarf gecko (Sphaerodactylus nicholsi), a male’s head-bob may be met with a female’s forelimb-lift of recognition. In the North American moose (Alces sp.), a male’s grunting call may be returned by a female’s higher-pitched wailing sound.
Ancient “you are there” messages predate linguistic communication and built a foundation for the basic dialogic pattern of language. They begin the back-and-forth, give-and-take dialogue that characterizes today’s sign languages and vocal speech. Nonverbal “you” may thus be considered a necessary, but not a sufficient, step toward language in Homo.
Step 4 (150 million years ago): Mammalian Emotion
Summary. With mammals, emotion becomes a volatile factor in intra- and interspecies communication. Housed in the limbic system, emotions are mammalian elaborations of vertebrate arousal patterns, in which dopamine, noradrenaline, serotonin, and other neurochemicals step-up or step-down the brain's activity level, as visible in body movements, facial expressions, and gestures. Emotional communication was shaped by social factors that reverberated in the cortex’s cingulate gyrus, for grooming with the hands, vocal calling, and maternal care of the young (MacLean 1990).
Affect. Face-to-face conversation is often accompanied by emotions such as happiness, sadness, anger, and uncertainty. These feelings may be telegraphed by nonverbal signs that include smiling, pouting, frowning, and shoulder shrugging. Emotion may also be audible in tone of voice. Spontaneous conversations are rarely dispassionate; more often than not they show affect.
In mammals and primates, affect is displayed by easily read emotion cues such as the cat’s (Felis catus) arched back, the dog’s (Canis familiaris) tail wag, and the chimpanzee’s (Pan troglodytes) fear grin. In humans, linguistic signing and speaking are often accompanied by emotion cues. American Sign Language’s hand signals for “Who?”, “What?” and “Why?”, for example, may be given with a signer’s eyebrows lowered in puzzlement or uncertainty.
Social jeopardy. One may choose to speak or remain silent. According to Goffman (1967), the former choice can involve a feeling of personal risk. Goffman maintains that people place themselves in a state of social uncertainty or ”jeopardy” when they make a verbal statement. There is an element of fear that receivers might react negatively by laughing, scowling, or smirking in disapproval. As Levinas (1989) writes, “By offering a word, the subject putting himself forward lays himself open and, in a sense, prays [for a positive response]” (p. 149).
Morris (1967) adds that talk may be informative (“The milk is in the refrigerator”), exploratory (“Where do you work?”), mood sharing (“I feel bad for him”), or polite (“Nice day”). He calls statements in the latter category “grooming talk,” likening their use to the manual grooming contact of primates. Kringelbach and Berridge (2012) note that social pleasures include “. . . vital sensory features such as visual faces, touch features of grooming and caress, as well as in humans more abstract and cognitive features of social reward and relationship evaluation. These may be especially important triggers for the brain’s hedonic networks in human beings.”
Indeed, there is neurological evidence that talking is intrinsically pleasurable. Talk is most gratifying when subject matter pertains to oneself, as in self-disclosure. As Tamir and Mitchell (2012) learned in fMRI research: “Self-disclosure was strongly associated with increased activation in brain regions that form the mesolimbic dopamine [pleasure-reward] system, including the nucleus accumbens and ventral tegmental area.” Pell and colleagues have found evidence in right cerebral-hemisphere brain modules for decoding emotional sounds--a precursor module for vocal (e.g., giggles, growls, and sobs), and a more recent module for linguistic (words and phrases), prosody (Pell et al. 2015; see “Prosody” below, Step 15). Mammalian emotion represents another necessary, but not sufficient, step toward language in Homo.
Step 5 (150 million years ago): Mammalian Acrobatic Tongue
Summary. In mammals, motor areas of cerebral cortex governing tongue movement enlarged to provide greater control in chewing. Mobile mammalian tongues replaced the more rigid tongues of fish, amphibians, and reptiles. In chewing, the trick for a tongue is not to be bitten in the process. The mammalian tongue’s innate dexterity kept it safe from teeth and conferred, as a byproduct, an ability to articulate vowel sounds and consonants.
Food tossing. Before saying words the mammalian tongue had been a humble manager of "food tossing." Through acrobatic maneuvers, chewed morsels were distributed by tongue movements to premolars and molars for finer grinding and pulping.
Before mammals, tongue movements were limited to backward and forward. The mechanical function was to move food in the throat back toward the gullet. In mammals, working through the hypoglossal nerve (cranial 12), voluntary control of tongue movement was enabled by the frontal lobe’s primary motor cortex. In humans, voluntary control of mammalian-inspired tongue movements was recruited for speech. Regarding spoken language, therefore, tongue dexterity may be considered a necessary, but not sufficient, step toward vocalizing words in Homo.
Step 6 (65 million years ago): Primate Binocular Vision
Summary. A stereoscopic view makes physical objects more visibly “real.” Binocular vision is highly adapted in arboreal, tree climbing primates. Seeing branches, berries, and insects from two angles at once provides a greater depth of field than does monocular vision, and enables greater “object integrity.” Seen in the round, physical objects stand out and have a clearer, sharper image, a visually more objective presence to which verbal names may be affixed. In primates, modules of inferior temporal cortex work in tandem with the occipital lobe for better object recognition, heightened response to hand shapes and gestures (Steps 7 and 11), and the ability to recognize facial expressions (Step 9).
One of language’s paramount jobs is naming objects and describing their properties in space-time (Steps 11 and 13). Stereoscopic vision may thus be considered a necessary, but not a sufficient, condition for the origin of manually signed and spoken words in language.
Step 7 (65 million years ago): Primate Grasping Hands
Summary. Object integrity was further enhanced in primates by prehensile hands. In tandem with binocular imaging, grasping a tree limb with fingers and palms makes the branch seem more tangible still, and, eventually in humans, more name-worthy as well. Sensorimotor cortical brain areas serving hands enlarged and improved the primate facility of palpating, exploring, and manipulating physical objects.
The 27 bones, 33 muscles and 20 joints of the human hand originated some 400 million years ago from the lobe fins of early fishes known as rhipidistians. Primeval swim fins helped our aquatic ancestors paddle through Devonian seas in search of food and mates. In amphibians, forelimbs evolved as weight-bearing platforms for walking on land. In primates hands became grasping organs, and were singled out for upgrade as tactile antennae or "feelers."
Infancy. Human babies are born with the primate ability to grasp objects tightly in a climbing-related power grip. Later, they instinctively reach for items placed in front of them. Between 1-1/2 and 3 months, reflexive grasping is replaced by an ability to hold-on by choice. Voluntary reaching appears during the 4th and 5th months of age, and coordinated sequences of reaching, grasping, and handling objects are seen by 3-to-6 months, as fingertips and palms explore the textures, shapes, warmth, wetness, and dryness of the material world in their reach space(Chase and Rubin 1979).
By 5 months, as a prelude to more expressive mime (pantomime) cues, babies posture with arms and hands as if anticipating the size and hardness or softness of objects (Chase and Rubin 1979). Between 6 and 9 months, infants learn to grasp food items between the thumb and outer side of the index finger, in an apelike precursor of the precision grip. At this time, babies pull, pound, rub, shake, push, twist, and creatively manipulate objects to determine their look and feel.
Hands and objects. Eventually a baby's hands experiment not only with objects themselves but with component parts, as if curious to learn more about how things fit together (Chase and Rubin 1979). At one year, infants grasp objects between the tactile pads of thumb and index finger, in a more mature, distinctively human precision grip. Pointing with an extended index finger (Step 13) also begins at 12 months, as babies use the cue to refer to novel sights and sounds, and speak their first words.
Manual intellect and emotion. Today in humans, fingers (unlike flippers, claws, or hooves) link to intellectual modules and emotion centers of the brain. Not only can we thread a needle, for example, we can also pantomime the act of threading with our fingertips--or reward a child's successful threading with a gentle pat. The primate ability to palpate, explore, and manipulate physical objects with the hands is yet another necessary, but not sufficient, condition for manual signing and speech.
Step 8 (65 million years ago): Primate Dexterous Lips
Summary. When not opening or closing a mouth, fish lips are rigidly fixed in place. In mammals, lips become mobile and connected to enlarged sensorimotor centers designed to contract muscles to form a sphincter-like seal around a mother’s breast for sucking. In primates lips become more dexterous still, and are recruited for audiovisual signaling in vocal calls (as in Alouata sp., the howler monkey) and facial expressions (as in chimpanzees).
Precision. To the dexterity of primate lips, humans add even greater precision for speech. Lip movements for speaking are controlled by Broca’s premotor area via the frontal lobe’s primary motor cortex. The principal lip muscle, orbicularis oris, is a sphincter consisting of pars marginalis (beneath the margin of the lips themselves), and pars peripheralis (around the lips' periphery from the nostril bulbs to the chin). P. marginalis is uniquely developed in humans for speech.
Mirror neurons. In humans mirror neurons are present in the primary motor area, premotor system (including Broca’s area), and supplementary motor system (Kilner & Lemon 2013). In monkeys mirror neurons have been found to fire both when food is brought to the mouth with a hand and when others are seen performing the same actions. But “. . . the most effective visual stimuli in triggering [the actions],” Ferrari and colleagues note, “are communicative mouth gestures (e.g. lip smacking)” (Ferrari et al. 2003, p. 1703). “Some also fire,” they add, “when the monkey makes communicative gestures. These findings extend the notion of mirror system from hand to mouth action and suggest that area F5, the area considered to be the homologue of human Broca's area, is also involved in communicative functions” (p. 1703). Thus, well before vocal or gestural language itself, primate lips and hands had been pre-adapted for social expression.
Consonants and vowels. In speaking, lips form bilabial English consonants--such as /b/, /p/, /m/, and /w/--in which respiratory airflow is stopped or restricted. Lips also form the rounded English vowels /o/ and /u/. Words with bilabial consonants in Asian languages include ”peeyah” (Burmese “pya,” bird), “beeyah” (Tibetan “bia,” bird), and “barf” (Brahui “barf,” snow; Ruhlen 1994, p. 44). Also in Asian languages, words with rounded vowels include “shayool” (Yukaghir “seul,” stone), “toe” (Tibetan “to,” stone), and “geyou” (Yaou “gyou,” stone; Ruhlen 1994, p. 44). Without their dexterous primate lips, humans would be unable to produce such sounds. Thus, dexterous lips may be considered a necessary, but not a sufficient, condition for the origin of language.
Step 9 (35-40 million years ago): Higher Primate Facial Communication
Summary. Higher primate (Anthropoidea) precursors had an enlarged visual cortex on the occipital lobe for processing color vision and depth. Today the anthropoid's is the most complex visual cortex yet developed, with anatomically separate areas for analyzing form, coordinating hand-and-eye movements, and recognizing faces. In human anthropoids, a few nerve cells in the lower temporal lobe are narrowly specialized to respond only to hands and faces (Kandel et al. 1991, p. 459).
Reading hand gestures and facial expressions enabled listeners to discern emotion behind signed and spoken words. Gestures and facial cues add emotion through increased levels of the social-bond-stimulating neuropeptides oxytocin and vasopressin. Faces are decoded in the anterior inferotemporal cortex; facial familiarity registers in the superior temporal polysensory area (Young & Yamane 1992). Emotional impacts of facial messages register in the amygdala.
A synergistic relationship likely obtained between facial messaging and eye contact. Extended eye contact between speaker and listener in face-to-face conversations may have enhanced face reading. Face reading in turn likely heightened eye contact. Reading lips (Step 8) is especially germane in speech. Functional MRI studies of speaking show that visual cues afforded by lip movements activate areas of auditory cortex in normal hearing individuals (Calvert et al. 1997). Since face-to-face linguistic dialogue would not likely have developed without an ability to read facial expressions, it is proposed that facial cues represent a necessary, but not a sufficient, condition for language.
Step 10 (24 million years ago): Primate Food Sharing
Summary. Sharing food items provided a model for the give-and-take, back-and-forth turn-taking of language. Physical closeness occasioned by food-sharing likely stimulated maternal-offspring communication. As in later speaking, food-sharing had a clearly emotional dimension. Both forms of expression are made more pleasurable by raised levels of the neuropeptides oxytocin and vasopressin. As indicated above (Step 4), the brain’s cingulate cortex has been implicated in maternal caring, grooming, and audiovocal signaling (MacLean 1990), each of which contributed to eventual speech.
Primate food sharing is an extension of the mammalian practice of providing mother’s milk. Maternal sharing with offspring of foods in addition to milk is widespread, occurring in 39 species of primates out of 69 sampled (Jaeggi & Gurven 2013). Old World monkeys and prosimians are least likely, while New World monkeys, all ape species, and humans are most likely, to share food with offspring.
Grunts and girneys. Maestripieri (2011) proposes that adult female primates are attracted to an infant’s facial appearance and coo vocalizations, finding these signs emotionally pleasing as brain opioids and oxytocin are released. Females may respond to infants by lip-smacking and vocalizing with grunts and girneys. Grunts are “brief bark-like atonal sounds,” while girneys are “nasal ‘singing‘ noises” (Maestripieri 2011, p. 520).
Gibson suggests that language evolution may have begun with food-sharing and simple one-or-two-word sentences exchanged by mothers with offspring. Tool-use likely played a role in the exchange. Early hominid mothers, she notes “. . . may have extracted and processed foods using tools and then shared the food with offspring incapable of tool use themselves. Such food sharing may have selected for communication capacities similar to those of children learning to talk. . .” (Gibson 1993, p. 266). The back-and-forth, turn-taking pattern inherent in sharing food items--combined with its emotional closeness--may be necessary, but not sufficient, for later turn-taking in language.
Step 11 (2.6 million years ago): Human Tool Making
Summary. Humans use and make stone tools. Flaking a tool and uttering a word use some of the same and closely related brain areas. So nearly alike are neural pathways for manual dexterity and articulate speech that a stone tool may be deciphered as if it were a petrified phrase. English "handaxe," for example, and the perception of the worked stone for which it stands, both exist as mental concepts whose neural templates are linked in the brain. "When an object is seen or its name read, knowledge of attributes is activated automatically and without conscious awareness" (Martin et al. 1995, p. 102). Broca’s area, the premotor-cortex module that governs language production, has been implicated in tool-making as well (Stout and Chaminade 2011). As Hauser noted, "When we create an artifact such as a tool, we leave a physical trace of our thoughts" (2000, p. 22).
Intelligently fabricated. In accord with Gibson’s (1993) linkage of tool use and food sharing, there is general agreement that human artifacts and tools played a major role in the origin of language (Gibson and Ingold 1993). An artifact is a material object (e.g., a bifacial stone tool) deliberately fabricated by humankind. Like gestures, artifacts have a great deal to "say." That they are intelligently fabricated is evident in their deliberately patterned shape, grammatical syntax (structured arrangement of parts), and orderly negative entropy in design.
English artifact comes from Latin arte ("by skill") and factum ("made"; via the ancient Indo-European root dhe-, "to set," "put," derivatives of which include deed, did, and do; skill "by hand" is implied). The earliest known artifacts come from Africa. At numerous sites from that continent sharply flaked stone tools have been found, dating back some 2.6 million years before present (Gibbons 1997).
While chimpanzees use stone tools, they do not make them. In Africa, chimpanzees shell panda nuts (Panda oleosa) together in the Tai forest of Ivory Coast. The chimps socialize as they crack the nuts’ hard shells with heavy, unworked stones, carefully placing each nut in a knothole before smashing it. Young chimpanzees watch their mothers, and after years of trial and error, learn to master the stone technology and crack the shells on their own. The learning curve is steep, but mothers share panda nuts with their own offspring as the latter learn (Boesch and Boesch-Achermann 2000). While there is a visible give-and-take in the dialogue as mother and offspring share food and the chopping-stone tool, few vocalizations are given by either party.
Mental concepts. Speech involves the ability to pair stored mental concepts with incoming data from the senses. Ivan Pavlov observed dogs in his laboratory as they paired the sound of human footsteps (incoming data) with memories of meat (stored mental concepts). Not only did meat itself cause Pavlov's dogs to salivate, but mental concepts of meat--memories of mealtimes past--were also called up by the sound of human feet. Pairing one sensation with memories of another--the process of sensitization or associative learning--is a fundamental ability given even to sea slugs (Nudibranchia).
In humans, tool use likely increased mental concept formation. MRI studies reveal that children who make early, skilled use of the digits of the right hand (e.g., in playing the piano) develop larger areas in the left sensory cortex devoted to fingering (Karni et al. 1998). Thus, Pleistocene youngsters precociously introduced to tool making may have developed enhanced neural circuitry for the task.
Mirror neurons. There is growing evidence, as well, of a role for mirror neurons in speech. "Taken together,” Iacoboni (2008) writes, “all these data show that gestures precede speech and that mirror neurons are probably the critical brain cells in language development and language evolution" (p. 87). As Egolf notes: "Gestures lead then speech follows, suggesting further that mirror neurons are critical for speech and language development. The interdependence of speech and gesture dashes some cold water on the espoused dichotomy between verbal and nonverbal communication" (2012, p. 90).
Controlled by the prefrontal cortex, an ability to manage the sequence of body movements required for tool making was a likely necessary, but not a sufficient, precursor to articulate sequencing in language.
Step 12 (1.9 million years ago): Object Fancy
In more severe forms [of the grasping reflex], any visual target will elicit manual reaching followed by tight grasping. --M. Marsel Mesulam (1992, p. 696)
Summary. In genus Homo the manufacture of stone, bone, wood, and other material artifacts was followed by a curious attraction to the artifacts themselves called “object fancy” (Givens 2008, p. 190). Object fancy is the desire to pick up, handle, and hold a material object, especially a consumer product of elegant design. It includes the urge to touch, own, arrange, collect, display, or talk about a manufactured artifact. Rooted in the grasping reflex, object fancy involves a balance between the parietal lobe's control of object handling and the frontal lobe's "thoughtful detachment" from the material world of goods (Mesulam 1992, p. 697).
Material gestures. Human-made items call attention to themselves through their structured design. Products "speak" to us nonverbally as tangible, material gestures. Their design features (e.g., the shine, shape, and smoothness of a platinum bracelet) send compelling messages that capture our attention. We pick them up to answer their call.
Names. Dialogue with objects commences at infancy. Communication with and about material things begins around six months of age (Trevarthen 1977). This early interaction with objects takes place in a context of social communication with caregivers, in tandem with the latter’s words. Repeated pairing of diverse objects with parental linguistic labels reinforces the notion that the objects at hand have names.
The linguistic power of object names is clear in the case of Helen Keller. Blind and deaf at 19 months of age, Keller’s path to language was severely impaired. To compensate for the disabilities, her teacher would finger-spell letters into Keller’s hand for environmental items such as tap water, a household mug, and a toy doll. After weeks of finger-spelling names like “d-o-l-l” into Keller’s hand, she grasped the idea that the objects in her world had unique names. Understanding this basic fact enabled Keller ultimately to achieve linguistic competence.
Magnetic effect. According to Mesulam, there exists a "magnetic effect triggered by objects" that originates with the brain’s innate grasping reflex (1992, p. 697). Subsequently it involves a balance between the parietal lobe's control of object fancy, and the frontal lobe's inattention to material goods. In patients with frontal lobe lesions, the mere sight of an artifact is "likely to elicit the automatic compulsion to use it," while lesions in the parietal network "promote an avoidance of the extrapersonal world" (Mesulam 1992, p.697).
Stone tools. The extrapersonal world of artifacts begins with stone tools. Dated to 2.6 million years ago, among the earliest known consumer products are intentionally flaked Oldowan pebble tools from Ethiopia, produced by Homo habilis. By 1.6 million years ago, a more eloquent, fist-sized hand-axe bearing a standardized, symmetrical, leaf-shaped design was being chipped in East Africa by Homo erectus. Known as Acheulean bifaces, these artifacts exhibited “elegant bilateral symmetry and overall regularity of form” (Ingold 1993, p. 337).
A likely artistic concern with form may have exceeded functional needs, and these early artifacts--which have been found on three continents--likely had names as well. So beautifully constructed, some Acheulean specimens may have been regarded as heirlooms and exchanged, much as ornamental shell bracelets were given and taken in the Trobriand Island Kula trade (Malinowski 1922).
Consumer products. Since the Stone Age, the number of consumer products invented and used by Homo sapiens--from Silly Putty to interstate highways--has increased at a rate three times greater than biological evolution (Basalla 1988). As the human brain and body were shaped by natural selection, consumer goods adapted to the mind through a parallel process of product selection, rendering them ever more fluent, expressive, and fascinating to the senses.
As shopping malls attest, object fancy prospers in the modern world. The average U.S. household stockpiles a greater supply of consumer goods than its members use. By age five, the average U.S. child has owned some 250 toys (Rosemond 1992). Among three to five-year-old children in preschools, fights occur over property and little else (Blurton Jones 1967).
In contrast to Americans, Tasmanian islanders off the southeast coast of Australia are among people who made and used the fewest number of artifacts. In all, Tasmanians used a total of some 25 stone and wooden tools, fiber baskets, shell necklaces, and bark canoes (Diamond1993). And yet, the contrast between U.S. urban consumers and Tasmanians is not marked, since the total time spent handling, repairing, exchanging, and communicating about (and with) artifacts may be roughly the same everywhere.
Consider Tibet, where material goods are relatively scarce yet resident Buddhists spend hours a day spinning prayer wheels. Made of metal, wood, or paper, the wheels have verbal mantras (Om Mani Padme Hum) written on the outside and included within. Users turn the cylindrical wheels with their fingers and voice the mantras as they spin. Nowhere is the link between object fancy and spoken word more clearly evident.
Step 13 (1.9 million years ago): Pointing--“It is there” (Advent of “That”)
Summary. A referentially pointed finger shows that advanced centers of the neocortex have been engaged. As a skilled gesture, pointing involves the supplementary motor area (SMA, which programs the sequence of arm, hand, and finger movements), the premotor cortex (which orients the arm movements), and the primary motor cortex (which programs the direction a gesture may take). In turn, the frontal cortex receives visual information about persons, places, and things from the posterior parietal lobes. While the left lobe involves language processing, the right processes spatial information to guide a pointed finger in the right direction. Like aphasia (the inability to speak), apraxia is an inability to point. That both are brought on by injuries to the cortex’s left side marks the similarity between voluntary pointing and language.
Referential pointing. Extending an index finger to call attention to objects and features of the environment is a gesture unique to human beings and captive chimpanzees (Leavens et al. 2005). Since it refers to the outside world, the referential point is a high-level, language-like gesture. In human infants, the referential point first appears around 12 months of age in tandem with the first use of words. Prior to speech itself, pointing is a reassuring sign of an infant's language ability. While some animals, including honeybees, can refer to environmental features, only humans (and infrequently, chimps) point them out with fingers.
All four fingers (the thumb has its own extensor muscles) may be extended in a coordinated way by contracting the forearm's extensor digitorum muscle. The index finger, however, has an extra forearm muscle (extensor indicis), which enhances the neural control of its muscular ability to point.
Alternate pathways. Early pointing is clearly emotional as toddlers point to share excitement with adults nearby. An excited child may extend an index finger toward a butterfly or chirping bird as mother watches, smiles, and articulates the creature’s name. Later in life, the gesture is controlled by more recent, advanced non-emotional modules of the brain. Nerve fibers from the latter’s primary motor area link directly to motor neurons, enabling the index finger to move deliberately and with precision. Long nerve fibers descend in a "mental expressway" which bypasses ancient brain-stem paths and fall directly onto the pointing digit. This more advanced pointing shows direct cortical control, as its neural pathway detours around older interneuron routes of the spinal cord.
Indexing. In American Sign Language “indexing” is the practice of using an extended index finger to point out personal and object pronouns, such as “I/me,” “you/you all,” “he/she/they,” and “it/them.” Pointing at persons and objects is also used in Plains Indian Sign Language. There is agreement among psychologists that referential pointing is a key to the development of language in infants (Leavens et al. 2005). Butterfield has called pointing “the royal road to language” (Butterfield 2003, p. 9).
With pointing, the conceptual transition from a personal “I am here” (Step 2) and “You are there” (Step 3) to an impersonal “It is there” is complete. In addition to calling attention to personal “I/me” and “you,” in Step 13 the members of Homo call attention to an impersonal “that.”
“That,” a word used to identify a person, plant, animal, or object observed by a speaker, appears in Swadesh’s (1971) list of the world’s 100 basic words. Superimposing communication about objects upon the earlier social communication about “I/me” and “you” was a significant step forward in the evolution of language. Like “I” and “you,” the elementary origin of “that” words is attested by their often simple phonetic, monosyllabic quality. In Eurasian language families, for instance, “that” is expressed variously by “toe” (Uralic “to”), “ha” (Khoisan “ha”), and “ta” (Altaic “ta”; Ruhlen 1994, p. 65).
Object words, in contrast, tend to be polysyllabic and phonetically more complex. Examples include ”keyahk” (Burmese “kyauk,” stone), “dantan” (Avestan “dantan,” tooth), and “tooloog” (Altaic “tulug,” feather; Ruhlen 1994). Recall Gibson’s suggestion (Step 10) that language evolution may have begun with food-sharing and simple one-or-two-word sentences.
Palm-up-and-down gestures. Referential pointing is more recent than, and contrasts with, earlier palm-up and palm-down communicative human signs. The latter hand signals--which are still in use today--may be regarded as gestural fossils left over from the original vertebrate system of communication about matters of social relationship (for an overview, see Givens 2015). Palm-up-and-down gestures are remnants of the ancestral articulators and may be used to reflect back on the social messages human forebears exchanged before the advent of pointing, languages, and words.
Stimulated by humankind’s seeming fascination with tangible objects that can be held in the hand, and by the fabrication of material artifacts and stone tools, ancestors of Homo sapiens gradually extended the use of pectoral-related body movements and laryngeal vocalizations for social communication to communication about objects and their features, and to the interrelationships of these in space-time. The ancient bodily articulators for linguistic communication were likely there from the beginning. Indeed, human gestural and spoken language was superimposed upon the earlier prelinguistic system of vertebrate social communication to which--by their current widespread use in face-to-face conversations--palm-up-and-down gestures strongly allude.
Referential pointing may be considered a necessary, but not a sufficient, mechanism for the development of linguistic communication.
Step 14 (1.9 million years ago): Human Cranial Capacity Increase
Summary. With Homo erectus the human brain enlarged from the apelike brain size of pre-erectus hominids. The corticobulbar nerve tract evolved; corticobulbar pathways to the facial nerve (cranial VII) permitted intentional facial expressions such as the voluntary smile. Broca's cranial pathways grew from a Broca's-area homologue via corticobulbar pathways to multiple cranial nerves, permitting human speech production. Broca's spinal pathways also evolved. Broca's-area circuits passing through corticospinal pathways to cervical and thoracic spinal nerves permitted manual sign language and linguistic-like mime (pantomime) cues. A Wernicke’s-area homologue grew to process incoming speech-like sounds.
The human brain began to enlarge between Steps 11 and 15--after tool-making and before signed/spoken language. Substantial enlargement took place in the cerebral neocortex, in association cortices responsible for the cognition and motor planning required for manufacturing tools. Motor systems for voluntary control of hand, lip, and tongue movements enlarged. In charge of the sequencing required for tool-making, and later for speech, the prefrontal cortex also grew.
Along with the cortex, diverse subcortical brain areas enlarged for the hand-eye coordination needed in tool-making. The emotional limbic system grew in tandem with the cerebral cortex (Armstrong 1986; see Step 4), making Homo sapiens the most emotional, intelligent--and fluent--species on earth.
Regarding signed and spoken words, the increase in human cranial capacity may be regarded as a necessary and sufficient condition for the development of language.
Step 15 (200 thousand years ago): Sonorous Human Larynx
Summary. In this step human vocalization becomes increasingly melodic, harmonious, and oratorical. The rationale for vocal softness and melody most certainly involved serenading in courtship. As it became more verbally linguistic, human courtship signaling likely favored vocal tenderness over harshness. The former voice quality is contact-inviting while the latter promotes distance.
Unlike wooden or metal tubes of a pipe organ, the human windpipe is pliable and protean in its ability to change shape. Encased in cartilage, the vibrating vocal folds produce sounds modified by elastic, membranous tissues and supple ligaments, further modified within mobile, mucus-lined pharyngeal, nasal, and oral chambers of the head. The musicality of human voices is processed in the planum temporale, a cortical auditory area found only in great apes and Homo.
Prosody. Compared to the harsh, often screaming vocalizations of chimpanzees, laryngeal-speech sounds produced by humans are softer, more sonorous, and more melodic in tone. Exemplars of today’s voice qualities include the eloquence of Martin Luther King in his “I Have a Dream” speech, Maya Angelou’s lyrical reading of her poem, “Phenomenal Woman,” and Luciano Pavarotti’s operatic rendition of “Serenade.” Each is delivered with vocal melody and lyrical motions of the fingers and hands.
Linguists call the quasi-musical qualities of human speech prosody. English “prosody” comes from Greek prosoidia, “song sung to music” or “accent.” Linguistic prosody includes accentuation, phrasing, rhythm, stress, and the tonal qualities of speech. On the nonverbal side, prosody includes the duration, muscular tension, and rhythm of hand movements that accompany words. Vocal and gestural prosody play important roles in the production and perception of human communication. Through them we detect emotions such as happiness, sadness, anger, fear, and uncertainty (Step 4) in utterance and gesture.
Serenade. Evolutionary reasons for vocal softness and melody involve serenading in courtship. Recall that from the beginning of life, intra-species communication has served a reproductive function (Step 1). In living primates, vocalizations including the gorilla’s “pant grunt,” the lemur’s “moans” and “meows,” and the tarsier’s “chirruping” calls are auditory courting signals. Again, as courtship became more verbally linguistic in humans, its signaling likely favored vocal tenderness over vocal harshness. The former invites closeness and contact while the latter promotes distance and separation. As Love Signals noted, “In courtship a softer, higher-pitched voice--the voice adults use with young children and pets--communicates an attitude of personal caring. Its lighthearted tenor is cheerful, calming, and universally friendly” (Givens 2005, pp. 85-6).
That speech has a reproductive function is evident in changes in the human voice at puberty. At the onset of reproductive age, male voices deepen through a lowering of the larynx and significant enlargement of its vocal folds. Deeper vocalizations are a vertebrate ploy for males to seem stronger and more daunting to rivals. "The more threatened or aggressive an animal becomes,” Hopson writes, “the lower and harsher its voice turns--thus, the bigger it seems" (1980, p. 83). In courtship, meanwhile, deeper vocalizations can be attractive. Female bullfrogs, for instance, swim toward males with the deepest calls. In humans, deeper-voiced males have been found to father more offspring (Apicella, Feinberg, and Marlowe 2007).
Since the sonorous human larynx likely developed after the brain enlargement of Homo erectus, it is neither a necessary nor a sufficient reason for the origin of language, but rather is a modification after the fact. In this sense it is like writing, an extension of language but not a cause.
Conclusion: Verbal Areas (200 thousand years ago)
Added value. Each of the 15 language steps physically worked its way into tissues of the human nervous system. Adaptively, each step added value by conferring greater access to environmental energy (e.g., through food extraction via tools) and social resources (via cooperation facilitated through communication). Favoring survival--whether through chemical signs of presence, visible signs of emotion, or audible signs of food sharing--each step conferred an adaptive advantage. Across millions of years, those benefitting from innovations within a given step came to outnumber those who did not. Physical changes in the nervous system were thus passed ahead in time to the present day.
Synergy. Language is more than a simple sum of the 15 developmental steps outlined in this paper. An interplay among and between the steps--a synergy--is evident as well. Gibson (Step 10) suggests a synergy between food sharing and tools. Tool making and object fancy (Steps 11 and 12) may be synergistically linked, as may be binocular vision and facial messages (Steps 6 and 9). Emotion messages (Step 4) are synergistically linked to facial messages, food sharing, object fancy, and pointing (Steps 9, 10, 12, and 13, respectively). Future research on the interplay and possible synergy among language steps, played out over vast sums of time, would be helpful to explain the stunning linguistic fluency of our species.
Sequencing. Words are produced by articulated movements of the hands in signing and by the vocal tract in speech. Word order is overseen by circuits of prefrontal cortex, which guide the sequential mental processing needed to build an artifact or compose a worded phrase. Controlled by the frontal lobes, both hands and speech organs follow correct behavioral sequences required to articulate verbal statements and manufacture tools. Recall (Step 4) that emotional communication was shaped by social factors that reverberated in the cingulate gyrus for grooming and vocal calling. There is reliable evidence for distinct grooming sequences--for a richly patterned "grammatical" order--even in the facial-grooming behavior of mice (family Muridai; Stilwell and Fentress 2010).
The supplementary motor area (SMA) of the cerebral neocortex is involved in sequential processing, as well, both for verbal and for some nonverbal articulations (such as mime cues). In function, SMA coordinates and controls the sequencing of bimanual hand movements. Found only in primates, SMA has been well studied in humans and monkeys. Regarding the latter, "We have found a group of cells in the cerebral cortex of monkeys,” Tanji and Shima note, “whose activity is exclusively related to a sequence of multiple movements performed in a particular order. Such cellular activity exists in the supplementary motor area. . .” (1994, p. 413).
Among verbal areas proposed for language are three with little or no basis in neurology: (1) Language Acquisition Device (LAD), (2) Growth Point (GP), and (3) Language Instinct (LI). Proposed in 1965 by Chomsky, the LAD is an unidentified brain module that supposedly enables children to speak and understand the grammatical rules of speech. Introduced in 1992 by McNeill, the GP is an unidentified neural process in which, theoretically, speech, thought, and gesture are simultaneously unified. And, advanced in 1994 by Pinker, the LI is an unidentified mental module that presumably confers an innate ability to speak and understand words. Though provocative, none of these hypothetical verbal areas have empirical meaning in neuroscience.
From messaging molecules of cyanobacteria to prosodic features of manual signing and speech, pre-language- and language-scaffolding abilities have been programmed into the neuromuscular system. Human gestural and spoken communication was superimposed upon the earlier nonverbal systems of vertebrate social communication. Today’s linguistic channel reflects the earlier medium’s roles in self-assertion, species recognition, genetic reproduction, emotional expression, and attention to objects.
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