View source for Origin of speech

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{{Lead too short|date=July 2022}}
{{Use British English|date=July 2014}}
{{Linguistics|Topics}}
[[Image:Places of articulation.svg|thumb|(passive and active):<br />1. Exo-labial, 2. Endo-labial, 3. Dental, 4. Alveolar, 5. Post-alveolar, 6. Pre-palatal, 7. Palatal, 8. Velar, 9. Uvular, 10. Pharyngeal, 11. Glottal, 12. Epiglottal, 13. Radical, 14. Postero-dorsal, 15. Antero-dorsal, 16. Laminal, 17. Apical, 18. Sub-apical]]
The '''origin of speech''' differs from the [[origin of language]] because language is not necessarily spoken; it could equally be [[Written language|written]] or [[Sign language|signed]]. Speech is a fundamental aspect of human communication and plays a vital role in the everyday lives of humans. It allows them to convey thoughts, emotions, and ideas, and providing the ability to connect with others and shape collective reality.<ref>{{Cite book |title=Oxford English Dictionary, [[Noam Chomsky]]}}</ref><ref>[[Oxford English Dictionary]]</ref>

Many attempts have been made to explain scientifically how speech emerged in humans, although to date no theory has generated agreement.

Non-human primates, like many other animals, have evolved specialized mechanisms for producing sounds for purposes of social communication.<ref>Kelemen, G. (1963). Comparative anatomy and performance of the vocal organ in vertebrates. In R. Busnel (ed.), ''Acoustic behavior of animals.'' Amsterdam:  Elsevier, pp. 489–521.</ref> On the other hand, no monkey or ape uses its ''tongue'' for such purposes.<ref name="Riede 2005">{{Cite journal  | last1 = Riede | first1 = T. | last2 = Bronson | first2 = E. | last3 = Hatzikirou | first3 = H. | last4 = Zuberbühler | first4 = K. | title = Vocal production mechanisms in a non-human primate: morphological data and a model. | journal = [[J Hum Evol]] | volume = 48 | issue = 1 | pages = 85–96 |date=Jan 2005 | doi = 10.1016/j.jhevol.2004.10.002 | pmid = 15656937 | url = http://doc.rero.ch/record/278428/files/Riede_T.-Vocal_production_20170126133920-UY.pdf }}</ref><ref name="Riede Bronson 2006">{{cite journal |last1=Riede |first1=T. |last2=Bronson |first2=E. |last3=Hatzikirou |first3=H. |last4=Zuberbühler |first4=K. |title=Multiple discontinuities in nonhuman vocal tracts – A reply |journal=Journal of Human Evolution |date=February 2006 |volume=50 |issue=2 |pages=222–225 |doi=10.1016/j.jhevol.2005.10.005 }}</ref> The human species' unprecedented use of the tongue, lips and other moveable parts seems to place speech in a quite separate category, making its evolutionary emergence an intriguing theoretical challenge in the eyes of many scholars.<ref name="Fitch 2000" />

==Modality-independence==
[[Image:Brain Surface Gyri.SVG|thumb|Language Areas of the human brain. The [[angular gyrus]] is represented in orange, [[supramarginal gyrus]] is represented in yellow, [[Broca's area]] is represented in blue, [[Wernicke's area]] is represented in green and the [[auditory cortex|primary auditory cortex]] is represented in pink.]]
The term ''[[Modality (semiotics)|modality]]'' means the chosen representational format for encoding and transmitting information. A striking feature of language is that it is ''modality-independent.'' Should an impaired child be prevented from hearing or producing sound, its innate capacity to master a language may equally find expression in signing. [[Sign language]]s of the deaf are independently invented and have all the major properties of spoken language except for the modality of transmission.<ref>Stokoe, W. C. 1960. ''Sign language structure: an outline of the communicative systems of the American deaf.'' Silver Spring, MD: Linstock Press.</ref><ref>Bellugi, U. and E. S. Klima 1975. Aspects of sign language and its structure. In J. F. Kavanagh and J. E. Cutting (eds), ''The Role of Speech in Language.'' Cambridge, Massachusetts: The MIT Press, pp. 171 203.</ref><ref name="Hickok 1996">{{Cite journal  | last1 = Hickok | first1 = G. | last2 = Bellugi | first2 = U. | last3 = Klima | first3 = ES. | title = The neurobiology of sign language and its implications for the neural basis of language. | journal = Nature | volume = 381 | issue = 6584 | pages = 699–702 |date=Jun 1996 | doi = 10.1038/381699a0 | pmid = 8649515 | bibcode = 1996Natur.381..699H | s2cid = 27480040 }}</ref><ref name="Kegl 1999">{{Cite book|last1= Kegl|first1= Judy|last2= Senghas|first2= Ann|last3= Coppola|first3= Marie|chapter= Creation through Contact: Sign Language Emergence and Sign Language Change in Nicaragua|editor= Michel DeGraff|title= Language creation and language change: creolization, diachrony, and development|year= 1999|publisher= MIT Press|location= Cambridge, Massachusetts|isbn= 978-0-262-04168-3|oclc= 39508250}}</ref> From this it appears that the [[language center|language centres]] of the human brain must have evolved to function optimally, irrespective of the selected modality.

{{quotation|"The detachment from modality-specific inputs may represent a substantial change in neural organization, one that affects not only imitation but also communication; only humans can lose one modality (e.g. hearing) and make up for this deficit by communicating with complete competence in a different modality (i.e. signing)."|{{Citation|title=''Marc Hauser, Noam Chomsky, and W. Tecumseh Fitch, 2002. ''The Faculty of Language: What Is It, Who Has It, and How Did It Evolve?}}<ref name="Hauser 2002">{{cite journal |last1=Hauser |first1=M. D. |last2=Chomsky |first2=N |last3=Fitch |first3=WT |title=The Faculty of Language: What Is It, Who Has It, and How Did It Evolve? |journal=Science |date=22 November 2002 |volume=298 |issue=5598 |pages=1569–1579 |doi=10.1126/science.298.5598.1569 |pmid=12446899 }}</ref>}}[[File:Expression of the Emotions Figure 18.png|thumb|left|Figure 18 from [[Charles Darwin]]'s ''[[The Expression of the Emotions in Man and Animals]]''. Caption reads "Chimpanzee disappointed and sulky. Drawn from life by Mr. Wood".]]

Animal communication systems routinely combine visible with audible properties and effects, but none is modality-independent. For example, no vocally-impaired whale, dolphin, or songbird could express its song repertoire equally in visual display. Indeed, in the case of animal communication, message and modality are not capable of being disentangled. Whatever message is being conveyed stems from the intrinsic properties of the signal.

Modality independence should not be confused with the ordinary phenomenon of [[multimodality]]. Monkeys and apes rely on a repertoire of species-specific "gesture-calls" – emotionally-expressive vocalisations inseparable from the visual displays which accompany them.<ref name="Goodall 1986">{{Cite book | last1 = Goodall | first1 = Jane | title = The chimpanzees of Gombe : patterns of behavior | year = 1986 | publisher = Belknap Press of Harvard University Press | location = Cambridge, Massachusetts | isbn = 978-0-674-11649-8 | oclc = 12550961 | url = https://archive.org/details/chimpanzeesofgom00good }}</ref><ref>{{cite journal | last1 = Burling | first1 = R | year = 1993 | title = Primate calls, human language, and nonverbal communication | journal = Current Anthropology | volume = 34 | pages = 25–53 | doi=10.1086/204132| s2cid = 147082731 }}</ref> Humans also have species-specific gesture-calls – laughs, cries, sobs, etc. – together with involuntary gestures accompanying speech.<ref>Darwin. C. 1872. ''The Expression of the Emotions in Man and Animals.'' London: Murray.{{page needed|date=March 2019}}</ref><ref>Ekman, P. 1982. ''Emotion in the Human Face,'' 2nd Edition. Cambridge: Cambridge University Press.{{page needed|date=March 2019}}</ref><ref>McNeil, D. 1992. ''Hand and Mind. What gestures reveal about thought.'' Chicago and London: University of Chicago Press.{{page needed|date=March 2019}}</ref> Many animal displays are polymodal in that each appears designed to exploit multiple channels simultaneously.

The human linguistic property of modality independence is conceptually distinct from polymodality. It allows the speaker to encode the informational content of a message in a single channel whilst switching between channels as necessary. Modern city-dwellers switch effortlessly between the spoken word and writing in its various forms – handwriting, typing, [[email]], etc. Whichever modality is chosen, it can reliably transmit the full message content without external assistance of any kind. When talking on the [[telephone]], for example, any accompanying facial or manual gestures, however natural to the speaker, are not strictly necessary. When typing or manually signing, conversely, there is no need to add sounds. In many [[Australian Aboriginal culture]]s, a section of the population – perhaps women observing a ritual [[taboo]] – traditionally restrict themselves for extended periods to a silent (manually-signed) version of their language.<ref>{{cite book|last=Kendon|first=Adam|year=1988|title=Sign Languages of Aboriginal Australia|location=Cambridge|publisher=Cambridge University Press|isbn=0-521-36008-0}}{{Page needed|date=June 2022}}</ref> Then, when released from the taboo, these same individuals resume narrating stories by the fireside or in the dark, switching to pure sound without sacrifice of informational content.

==Evolution of the speech organs==
[[Image:Illu01 head neck.jpg|thumb|Human vocal tract]]
Speaking is the default modality for language in all cultures. Humans' first recourse is to encode their thoughts in sound – a method which depends on sophisticated capacities for controlling the lips, tongue and other components of the vocal apparatus.

The speech organs evolved in the first instance not for speech but for more basic bodily functions such as feeding and breathing. Nonhuman primates have broadly similar organs, but with different neural controls.<ref name="Fitch 2000">{{cite journal |last1=Fitch |first1=W.Tecumseh |title=The evolution of speech: a comparative review |journal=Trends in Cognitive Sciences |date=July 2000 |volume=4 |issue=7 |pages=258–267 |doi=10.1016/S1364-6613(00)01494-7 |pmid=10859570 |citeseerx=10.1.1.22.3754 |s2cid=14706592 }}</ref> Non-human apes use their highly-flexible, maneuverable tongues for eating but not for vocalizing. When an ape is not eating, fine motor control over its tongue is deactivated.<ref name="Riede 2005" /><ref name="Riede Bronson 2006" /> ''Either'' it is performing gymnastics with its tongue ''or'' it is vocalising; it cannot perform both activities simultaneously. Since this applies to [[mammal]]s in general, ''Homo sapiens'' are exceptional in harnessing mechanisms designed for [[Respiration (physiology)|respiration]] and [[ingestion]] for the radically different requirements of articulate speech.<ref>MacNeilage, Peter, 2008. ''The Origin of Speech.'' Oxford: Oxford University Press.{{page needed|date=March 2019}}</ref>

==Possible semi-aquatic adaptations==

Recent insights in human evolution – more specifically, human Pleistocene littoral evolution<ref name="Rhys-Evans Waterside Ape">{{cite book |last1=Rhys-Evans |first1=Peter |title=The Waterside Ape |date=29 July 2019 |publisher=CRC Press |isbn=9780367145484}}</ref> – may help understand how human speech evolved. One controversial suggestion is that certain pre-adaptations for spoken language evolved during a time when ancestral hominins lived close to river banks and lake shores rich in fatty acids and other brain-specific nutrients. Occasional wading or swimming may also have led to enhanced breath-control ([[Freediving|breath-hold diving]]). 

Independent lines of evidence suggest that "archaic" [[Homo]] spread intercontinentally along the [[Indian Ocean]] shores (they even reached overseas islands such as [[Flores]]) where they regularly dived for [[Littoral zone|littoral]] foods such as shell- and [[crayfish]],<ref name="joordens et al">{{cite journal |last1=Joordens |first1=Josephine C. A. |title=Homo erectus at Trinil on Java used shells for tool production and engraving |journal=Nature |date=3 December 2014 |volume=518 |issue=7538 |pages=228–231 |doi=10.1038/nature13962 |pmid=25470048 |bibcode=2015Natur.518..228J |s2cid=4461751 |url=https://www.nature.com/articles/nature13962 |access-date=11 June 2021}}</ref> which are extremely rich in brain-specific nutrients, explaining Homo's brain enlargement.<ref name="cunnane 2010">{{cite book |last1=Stephen |first1=Cunnane |title=Human brain evolution : the influence of freshwater and marine food resources |date=2010 |publisher=Wiley-Blackwell |location=Hoboken, N.J. |isbn=978-0470452684}}</ref> [[Shallow diving]] for seafoods requires voluntary airway control, a prerequisite for spoken language. Seafood such as shellfish generally does not require biting and chewing, but [[Stone tool|stone tool use]] and suction feeding. This finer control of the oral apparatus was arguably another biological pre-adaptation to human speech, especially for the production of consonants.<ref name="verhaegen munro 2004">{{cite journal |last1=Verhaegen |first1=M. |last2=Munro |first2=S. |title=Possible preadaptations to speech. A preliminary comparative |journal=Human Evolution |date=January 2004 |volume=19 |issue=1 |pages=53–70 |doi=10.1007/BF02438909 |s2cid=86519517 |url=https://link.springer.com/article/10.1007/BF02438909 |access-date=11 June 2021}}</ref>

===Tongue===
[[Image:Spectrogram -iua-.png|thumb|[[Spectrogram]] of American English vowels {{IPA|[i, u, ɑ]}} showing the formants ''f''<sub>1</sub> and ''f''<sub>2</sub>]]
The word "language" derives from the Latin ''lingua,'' "tongue". [[Phoneticians]] agree that the tongue is the most important speech articulator, followed by the lips. A [[natural language]] can be viewed as a particular way of using the tongue to express thought.

The human tongue has an unusual shape. In most mammals, it is a long, flat structure contained largely within the mouth. It is attached at the rear to the [[hyoid bone]], situated below the oral level in the [[pharynx]]. In humans, the tongue has an almost circular [[Sagittal plane|sagittal]] (midline) contour, much of it lying vertically down an extended [[pharynx]], where it is attached to a hyoid bone in a lowered position. Partly as a result of this, the horizontal (inside-the-mouth) and vertical (down-the-throat) tubes forming the supralaryngeal vocal tract (SVT) are almost equal in length (whereas in other species, the vertical section is shorter). As humans move their jaws up and down, the tongue can vary the cross-sectional area of each tube independently by about 10:1, altering formant frequencies accordingly. That the tubes are joined at a right angle permits pronunciation of the [[vowel]]s '''[i], [u]''' and '''[a]''', which nonhuman primates cannot do.<ref>{{cite journal |last1=Lieberman |first1=Philip |last2=Crelin |first2=Edmund S. |last3=Klatt |first3=Dennis H. |title=Phonetic Ability and Related Anatomy of the Newborn and Adult Human, Neanderthal Man, and the Chimpanzee |journal=American Anthropologist |date=June 1972 |volume=74 |issue=3 |pages=287–307 |doi=10.1525/aa.1972.74.3.02a00020 }}</ref> Even when not performed particularly accurately, in humans the articulatory gymnastics needed to distinguish these vowels yield consistent, distinctive acoustic results, illustrating the quantal{{Clarify|reason=What do you mean by "quantal"?|date=June 2022}} nature of human speech sounds.<ref>Stevens, K. N. 1972. The quantal nature of speech: Evidence from articulatory-acoustic data. In P. B. Denes and E. E. David, Jr. (eds.), ''Human Communication: A unified view.'' New York: McGraw-Hill, pp. 51–66.</ref> It may not be coincidental that '''[i], [u]''' and '''[a]''' are the most common vowels in the world's languages.<ref name=":2">Ladefoged, P. and Maddieson, I. 1996. ''The Sounds of the World's Languages.'' Oxford: Blackwell.</ref> Human tongues are a lot shorter and thinner than other mammals and are composed of a large number of muscles, which helps shape a variety of sounds within the oral cavity. The diversity of sound production is also increased with the human’s ability to open and close the airway, allowing varying amounts of air to exit through the nose. The fine motor movements associated with the tongue and the airway, make humans more capable of producing a wide range of intricate shapes in order to produce sounds at different rates and intensities.<ref name=":0">{{Cite book|url=http://www.dsglynn.univ-paris8.fr/Reading1_from_Yule_2014_-_The_Study_of_Language.pdf|title=The Study of Language|last=Yule|first=George|date=2014|publisher=Cambridge University Press|isbn=9781107044197|via=www.dsglynn.univ-paris8.fr}}</ref>

===Lips===
In humans, the lips are important for the production of [[stop consonant|stops]] and [[Fricative consonant|fricatives]], in addition to [[vowel]]s. Nothing, however, suggests that the lips evolved for those reasons. During [[Evolution of primates|primate evolution]], a shift from [[Nocturnality|nocturnal]] to [[Diurnality|diurnal]] activity in [[tarsier]]s, monkeys and apes (the [[Haplorhini|haplorhines]]) brought with it an increased reliance on vision at the expense of [[Sense of smell|olfaction]]. As a result, the snout became reduced and the [[rhinarium]] or "wet nose" was lost. The muscles of the face and lips consequently became less constrained, enabling their co-option to serve purposes of facial expression. The lips also became thicker, and the oral cavity hidden behind became smaller.<ref name=":0" /> Hence, according to Ann MacLarnon, "the evolution of mobile, muscular lips, so important to human speech, was the exaptive result of the evolution of diurnality and visual communication in the common ancestor of haplorhines".<ref>MacLarnon, A. 2012. The anatomical and physiological basis of human speech production: adaptations and exaptations. In M. Tallerman and K. .Gibson (eds.), ''The Oxford Handbook of Language Evolution.'' Oxford: Oxford University Press, pp. 224-235.</ref> It is unclear whether human lips have undergone a more recent adaptation to the specific requirements of speech.

===Respiratory control===
Compared with nonhuman primates, humans have significantly enhanced control of breathing, enabling exhalations to be extended and inhalations shortened as we speak. Whilst we are speaking, [[Intercostal muscles|intercostal]] and [[Abdominal muscle|interior abdominal muscles]] are recruited to expand the [[thorax]] and draw air into the lungs, and subsequently to control the release of air as the lungs deflate. The muscles concerned are markedly more [[innervated]] in humans than in nonhuman primates.<ref>MacLarnon, A. M. (1993). The vertebral canal. In A. Walker and R. Leakey (eds.), ''The Nariokotome ''Homo erectus'' skeleton.'' Cambridge, Massachusetts: Harvard University Press, 359–90.</ref> Evidence from fossil hominins suggests that the necessary enlargement of the [[vertebral canal]], and therefore [[spinal cord]] dimensions, may not have occurred in ''[[Australopithecus]]'' or ''[[Homo erectus]]'' but was present in the [[Neanderthal]]s and early modern humans.<ref name="MacLarnon 1999">{{cite journal |vauthors=MacLarnon AM, Hewitt GP |title=The evolution of human speech: the role of enhanced breathing control |journal=Am. J. Phys. Anthropol. |volume=109 |issue=3 |pages=341–63 |date=July 1999 |pmid=10407464 |doi=10.1002/(SICI)1096-8644(199907)109:3<341::AID-AJPA5>3.0.CO;2-2 }}</ref><ref name="Maclarnon Hewitt 2004">{{cite journal |last1=MacLarnon |first1=Ann |last2=Hewitt |first2=Gwen |year=2004 |title=Increased breathing control: Another factor in the evolution of human language |journal=Evolutionary Anthropology: Issues, News, and Reviews |volume=13 |issue=5 |pages=181–197 |doi=10.1002/evan.20032 |s2cid=84625135}}</ref>

===Larynx===
[[File:Larynx external en.svg|thumb|Anatomy of the larynx, [[anatomical terms of location|anterolateral]] view]]
[[File:Illu larynx.jpg]]

The '''[[larynx]]''' or voice box is an organ in the neck housing the [[vocal folds]], which are responsible for [[phonation]]. In humans, the larynx is ''descended,'' it is positioned lower than in other primates. This is because the evolution of humans to an upright position shifted the head directly above the spinal cord, forcing everything else downward. The repositioning of the larynx resulted in a longer cavity called the pharynx, which is responsible for increasing the range and clarity of the sound being produced. Other primates have almost no pharynx; therefore, their vocal power is significantly lower.<ref name=":0" /> Humans are not unique in this respect: goats, dogs, pigs and [[tamarin]]s lower the larynx temporarily, to emit loud calls.<ref name="Fitch. WT 2000">{{Cite journal|last1= Fitch|first1= W.T.|title= The phonetic potential of nonhuman vocal tracts: comparative cineradiographic observations of vocalizing animals|journal= Phonetica|volume= 57|issue= 2–4|pages= 205–18|year= 2000|doi= 10.1159/000028474|pmid= 10992141|s2cid= 202652500}}</ref> Several deer species have a permanently lowered larynx, which may be lowered still further by males during their [[Roar (vocalization)|roaring displays]].<ref name="Fitch 2001">{{Cite journal|last1= Fitch|first1= W.T.|last2= Reby|first2= D.|title= The descended larynx is not uniquely human|journal= Proc Biol Sci|volume= 268|issue= 1477|pages= 1669–75|date= Aug 2001|doi= 10.1098/rspb.2001.1704|pmid= 11506679|pmc= 1088793}}</ref> Lions, jaguars, cheetahs and domestic cats also do this.<ref name="Weissengruber 2002">{{Cite journal|last1= Weissengruber|first1= G.E.|last2= Forstenpointner|first2= G.|last3= Peters|first3= G.|last4= Kübber-Heiss|first4= A.|last5= Fitch|first5= W.T.|title= Hyoid apparatus and pharynx in the lion (Panthera leo), jaguar (Panthera onca), tiger (Panthera tigris), cheetah (Acinonyxjubatus) and domestic cat (Felis silvestris f. catus)|journal= J Anat|volume= 201|issue= 3|pages= 195–209|date= Sep 2002|doi= 10.1046/j.1469-7580.2002.00088.x|pmid= 12363272|pmc= 1570911}}</ref> However, laryngeal descent in nonhumans (according to [[Philip Lieberman]]) is not accompanied by descent of the hyoid; hence the tongue remains horizontal in the oral cavity, preventing it from acting as a pharyngeal articulator.<ref name="Lieberman 2007">{{cite journal|last1=Lieberman|first1=Philip|title=The Evolution of Human Speech: Its Anatomical and Neural Bases|journal=Current Anthropology|volume=48|issue=1|year=2007|pages=39–66|url=http://www.cog.brown.edu/people/lieberman/pdfFiles/Lieberman%20P.%202007.%20The%20evolution%20of%20human%20speech,%20Its%20anatom.pdf|doi=10.1086/509092|s2cid=28651524|access-date=2012-07-22|archive-date=2014-06-11|archive-url=https://web.archive.org/web/20140611203314/http://www.cog.brown.edu/people/lieberman/pdfFiles/Lieberman%20P.%202007.%20The%20evolution%20of%20human%20speech,%20Its%20anatom.pdf|url-status=dead}}</ref>

[[File:Gray1194.png|thumb|Anterolateral view of head and neck]]
Despite all this, scholars remain divided as to how "special" the human vocal tract really is. It has been shown that the larynx does descend to some extent during development in chimpanzees, followed by hyoidal descent.<ref name="Nishimura 2006">{{Cite journal  | last1 = Nishimura | first1 = T. | last2 = Mikami | first2 = A. | last3 = Suzuki | first3 = J. | last4 = Matsuzawa | first4 = T. | title = Descent of the hyoid in chimpanzees: evolution of face flattening and speech. | journal = J Hum Evol | volume = 51 | issue = 3 | pages = 244–54 |date=Sep 2006 | doi = 10.1016/j.jhevol.2006.03.005 | pmid = 16730049 }}</ref> As against this, Philip Lieberman points out that only humans have evolved permanent and substantial laryngeal descent in association with hyoidal descent, resulting in a curved tongue and two-tube vocal tract with 1:1 proportions.{{Citation needed|date=June 2022}} Uniquely in the human case, simple contact between the [[epiglottis]] and [[Velum interpositum|velum]] is no longer possible, disrupting the normal mammalian separation of the respiratory and digestive tracts during swallowing. Since this entails substantial costs – increasing the risk of choking whilst swallowing food – we are forced to ask what benefits might have outweighed those costs. Some claim the clear benefit must have been speech, but other contest this. One objection is that humans are in fact not seriously at risk of choking on food: medical statistics indicate that accidents of this kind are extremely rare.<ref>M. Clegg 2001. The Comparative Anatomy and Evolution of the Human Vocal Tract Unpublished thesis, University of London.</ref> Another objection is that in the view of most scholars, speech as we know it emerged relatively late in human evolution, roughly contemporaneously with the emergence of ''Homo sapiens.''<ref name="Perreault 2012">{{Cite journal  | last1 = Perreault | first1 = C. | last2 = Mathew | first2 = S. | title = Dating the origin of language using phonemic diversity. | journal = PLOS ONE | volume = 7 | issue = 4 | pages = e35289 | year = 2012 | doi = 10.1371/journal.pone.0035289 | pmid = 22558135| pmc = 3338724 | bibcode = 2012PLoSO...735289P | doi-access = free }}</ref> A development as complex as the reconfiguration of the human vocal tract would have required much more time, implying an early date of origin. This discrepancy in timescales undermines the idea that human vocal flexibility was initially driven by selection pressures for speech.

At least one orangutan has demonstrated the ability to control the voice box.<ref>{{cite web |title=Orangutan's Vocal Feats Hint At Deeper Roots of Human Speech |author=Jon Hamilton |url=https://www.npr.org/sections/health-shots/2017/03/14/518170608/orangutans-vocal-feats-hint-at-deeper-roots-of-human-speech |date=14 March 2017 |website=NPR}}</ref>

=== The size exaggeration hypothesis ===
To lower the larynx is to increase the length of the vocal tract, in turn lowering [[formant]] frequencies so that the voice sounds "deeper" – giving an impression of greater size. [[John Ohala]] argued that the function of the lowered larynx in humans, especially males, is probably to enhance threat displays rather than speech itself.<ref>John J. Ohala, 2000. [http://linguistics.berkeley.edu/~ohala/papers/lowered_larynx.pdf The irrelevance of the lowered larynx in modern Man for the development of speech.] Paris, ENST: ''The Evolution of Language,'' pp. 171-172.</ref> Ohala pointed out that if the lowered larynx were an adaptation for speech, we would expect adult human males to be better adapted in this respect than adult females, whose larynx is considerably less low. In fact, females invariably outperform males in verbal tests, falsifying this whole line of reasoning.{{Citation needed|date=August 2022}} [[W. Tecumseh Fitch|William Tecumseh Fitch]] likewise argues that this was the original selective advantage of laryngeal lowering in humans. Although, according to Fitch, the initial lowering of the larynx in humans had nothing to do with speech, the increased range of possible formant patterns was subsequently co-opted for speech. Size exaggeration remains the sole function of the extreme laryngeal descent observed in male deer. Consistent with the size exaggeration hypothesis, a second descent of the larynx occurs at puberty in humans, although only in males. In response to the objection that the larynx is descended in human females, Fitch suggests that mothers vocalising to protect their infants would also have benefited from this ability.<ref>Fitch, W. T. (2002). Comparative vocal production and the evolution of speech: Reinterpreting the descent of the larynx. In A. Wray (ed.), ''The Transition to Language.'' Oxford: Oxford University Press, pp. 21–45.</ref>

===Neanderthal speech===
[[File:Gray186.png|thumb|Hyoid bone&nbsp;– anterior surface, enlarged]]

Most specialists credit the Neanderthals with speech abilities not radically different from those of modern ''Homo sapiens''. An indirect line of argument is that their [[tool]]making and [[Hunting|hunting tactics]] would have been difficult to learn or execute without some kind of speech.<ref>Wynn & Coolidge, p.27</ref> A recent extraction of [[DNA]] from Neanderthal bones indicates that Neanderthals had the same version of the [[FOXP2]] gene as modern humans. This gene, mistakenly described as the "grammar gene", plays a role in controlling the orofacial movements which (in modern humans) are involved in speech.<ref>{{Cite news|first=Nicholas |last=Wade |author-link=Nicholas Wade |date=19 October 2007 |title=Neanderthals Had Important Speech Gene, DNA Evidence Shows |url=https://www.nytimes.com/2007/10/19/science/19speech-web.html |work=[[The New York Times]] |access-date=18 May 2009}}</ref>

During the 1970s, it was widely believed that the Neanderthals lacked modern speech capacities.<ref>{{Cite journal |first1=Philip |last1=Lieberman |first2=Edmund S. |last2=Crelin |date=Spring 1971 |title=On the Speech of Neanderthal Man |journal=Linguistic Inquiry |volume=2 |issue=2 |pages=203–222 |url=http://www.haskins.yale.edu/Reprints/HL0104.pdf |access-date=2019-09-03 |jstor=4177625 |archive-date=2016-03-06 |archive-url=https://web.archive.org/web/20160306121006/http://www.haskins.yale.edu/Reprints/HL0104.pdf |url-status=dead }}</ref> It was claimed that they possessed a hyoid bone so high up in the vocal tract as to preclude the possibility of producing certain vowel sounds.

The hyoid bone is present in many mammals. It allows a wide range of tongue, pharyngeal and laryngeal movements by bracing these structures alongside each other in order to produce variation.<ref name="Nishimura 2003">{{Cite journal  | last1 = Nishimura | first1 = T. | last2 = Mikami | first2 = A. | last3 = Suzuki | first3 = J. | last4 = Matsuzawa | first4 = T. | title = Descent of the larynx in chimpanzee infants. | journal = Proc Natl Acad Sci U S A | volume = 100 | issue = 12 | pages = 6930–3 | date=Jun 2003 | doi = 10.1073/pnas.1231107100 | pmid = 12775758 | pmc = 165807| bibcode = 2003PNAS..100.6930N | doi-access = free }}</ref> It is now realised that its lowered position is not unique to ''Homo sapiens'', whilst its relevance to vocal flexibility may have been overstated: although men have a lower larynx, they do not produce a wider range of sounds than women or two-year-old babies. There is no evidence that the larynx position of the Neanderthals impeded the range of vowel sounds they could produce.<ref>{{cite journal | last1 = Boë | first1 = L.J. |display-authors=etal  | year = 2002 | title = The potential of Neandertal vowel space was as large as that of modern humans | journal = Journal of Phonetics | volume = 30 | issue = 3| pages = 465–484 | doi=10.1006/jpho.2002.0170}}</ref> The discovery of a modern-looking hyoid bone of a Neanderthal man in the [[Kebara Cave]] in [[Israel]] led its discoverers to argue that the Neanderthals had a descended [[larynx]], and thus human-like [[speech]] capabilities.<ref name="Arensburg 1990">{{Cite journal  | last1 = Arensburg | first1 = B. | last2 = Schepartz | first2 = LA. | last3 = Tillier | first3 = AM. | last4 = Vandermeersch | first4 = B. | last5 = Rak | first5 = Y. | title = A reappraisal of the anatomical basis for speech in Middle Palaeolithic hominids. | journal = Am J Phys Anthropol | volume = 83 | issue = 2 | pages = 137–146 |date=Oct 1990 | doi = 10.1002/ajpa.1330830202 | pmid = 2248373 }}</ref><ref>{{Cite journal|vauthors=Arensburg B, Tillier AM, Vandermeersch B, Duday H, Schepartz LA, Rak Y |title=A Middle Palaeolithic human hyoid bone |journal=Nature |volume=338 |issue=6218 |pages=758–60 |date=April 1989 |pmid=2716823 |doi=10.1038/338758a0 |bibcode=1989Natur.338..758A |s2cid=4309147 }}</ref> However, other researchers have claimed that the [[Morphology (biology)|morphology]] of the hyoid is not indicative of the larynx's position.<ref name="Fitch 2000" /> It is necessary to take into consideration the [[skull base]], the [[mandible]], the [[cervical vertebrae]] and a cranial reference plane.<ref>Granat et al., Hyoid bone and larynx in Homo. Estimated position by biometrics, Biom. Hum. et Anthropolol., 2006, 24, 3-4, 243–255.</ref><ref>Boë, L.J. et al., Variation and prediction of the hyoid bone position for modern Man and Neanderthal, Biom. Hum. et Anthropolol., 2006, 24, 3-4, 257–271</ref>

The morphology of the [[outer ear|outer]] and [[middle ear]] of [[Middle Pleistocene]] hominins from [[Atapuerca, Province of Burgos|Atapuerca]], Spain, believed to be proto-Neanderthal, suggests they had an auditory sensitivity similar to modern humans and very different from chimpanzees. They were probably able to differentiate between many different speech sounds.<ref>{{Cite journal|author1=Martínez I. |author2=Rosa M. |author3=Arsuaga J.L. |author4=Jarabo P. |author5=Quam R. |author6=Lorenzo C. |author7=Gracia A. |author8=Carretero J.M. |author9=Bermúdez de Castro J.M. |author10=Carbonell E. |title=Auditory capacities in Middle Pleistocene humans from the Sierra de Atapuerca in Spain |journal=[[Proceedings of the National Academy of Sciences]] |volume=101 |issue=27 |pages=9976–81 |date=July 2004 |pmid=15213327 |pmc=454200 |doi=10.1073/pnas.0403595101 |bibcode=2004PNAS..101.9976M |doi-access=free }}</ref>

====Hypoglossal canal====
{{Infobox anatomy|type=nerve
| Name        = Hypoglossal nerve
| Latin       = nervus hypoglossus
| Image       = Gray794.png
| Caption     = Hypoglossal nerve, [[cervical plexus]], and their branches
| Image2      = 
| Caption2    = 
| Innervates  = 
| BranchFrom  = 
| BranchTo    = 
}}
The [[hypoglossal nerve]] plays an important role in controlling movements of the tongue. In 1998, a research team used the size of the [[hypoglossal canal]] in the base of fossil skulls in an attempt to estimate the relative number of [[nerve fibres]], claiming on this basis that Middle Pleistocene hominins and Neanderthals had more fine-tuned tongue control than either [[Australopithecine]]s or apes.<ref>{{cite journal | last1 = Kay | first1 = R. F. | last2 = Cartmill | first2 = M. | last3 = Balow | first3 = M. | year = 1998 | title = The hypoglossal canal and the origin of human vocal behavior | journal = Proceedings of the National Academy of Sciences of the USA | volume = 95 | issue = 9| pages = 5417–5419 | doi=10.1073/pnas.95.9.5417| pmid = 9560291 | pmc = 20276 | bibcode = 1998PNAS...95.5417K | doi-access = free }}</ref> Subsequently, however, it was demonstrated that hypoglossal canal size and nerve sizes are not correlated,<ref>{{cite journal | last1 = DeGusta | first1 = D. | last2 = Gilbert | first2 = W. H. | last3 = Turner | first3 = S. P. | year = 1999 | title = Hypoglossal canal size and hominid speech | journal = Proceedings of the National Academy of Sciences of the USA | volume = 96 | issue = 4| pages = 1800–1804 | doi=10.1073/pnas.96.4.1800| pmid = 9990105 | pmc = 15600 | bibcode = 1999PNAS...96.1800D | doi-access = free }}</ref> and it is now accepted that such evidence is uninformative about the timing of human speech evolution.<ref>{{cite journal | last1 = Jungers | first1 = W. L. | last2 = Pokempner | first2 = A. A. | last3 = Kay | first3 = R. F. | last4 = Cartmill | first4 = M. | year = 2003 | title = Hypoglossal canal size in living hominoids and the evolution of human speech | journal = Human Biology | volume = 75 | issue = 4| pages = 473–484 | doi=10.1353/hub.2003.0057 | pmid = 14655872| s2cid = 30777048 }}</ref>

===Distinctive features theory===
{{IPA vowels|class=floatright}}
According to one influential school,<ref>Jakobson, R., Gunnar, C., Fant, M. and Halle, M. 1952. ''Preliminaries to Speech Analysis.'' Cambridge, Massachusetts: MIT Press.</ref><ref>Jakobson, R. and M. Halle 1956. ''Fundamentals of Language.'' The Hague: Mouton.</ref> the human vocal apparatus is intrinsically digital on the model of a keyboard or digital computer (see below). Nothing about a chimpanzee's vocal apparatus suggests a digital keyboard, notwithstanding the anatomical and physiological similarities. This poses the question as to when and how, during the course of human evolution, the transition from analog to digital structure and function occurred.

The human supralaryngeal tract is said to be digital in the sense that it is an arrangement of moveable toggles or switches, each of which, at any one time, must be in one state or another. The vocal cords, for example, are either vibrating (producing a sound) or not vibrating (in silent mode). By virtue of simple physics, the corresponding [[distinctive feature]] – in this case, "voicing" – cannot be somewhere in between. The options are limited to "off" and "on". Equally digital is the feature known as "[[Nasalization|nasalisation]]". At any given moment the [[soft palate]] or velum either allows or does not allow sound to resonate in the [[Nasal cavity|nasal chamber]]. In the case of lip and tongue positions, more than two digital states may be allowed.

The theory that speech sounds are composite entities constituted by complexes of binary phonetic features was first advanced in 1938 by the Russian linguist [[Roman Jakobson]].<ref>Jakobson, R. 1938. "Observations sur le classement phonologiques des consonnes", in ''Proceedings of the 3rd International Congress of Phonetic Sciences,'' Ghent.</ref> A prominent early supporter of this approach was [[Noam Chomsky]], who went on to extend it from phonology to language more generally, in particular to the study of [[syntax]] and [[semantics]].<ref>Chomsky, N. 1957. ''Syntactic Structures.'' The Hague: Mouton.</ref><ref>Chomsky, N. 1964 [1962]. The logical basis of linguistic theory. In H.G. Lunt (ed.), The Proceedings of the Ninth International Congress of Linguists. The Hague: Mouton, pp. 914-77.</ref><ref>Chomsky, N. and Halle, M. 1968. ''The Sound Pattern of English.'' New York: Harper and Row.</ref> In his 1965 book, ''[[Aspects of the Theory of Syntax]],''<ref>Chomsky, N. 1965. ''Aspects of the Theory of Syntax.'' Cambridge, Massachusetts: MIT Press, pp. 148-192.</ref> Chomsky treated semantic concepts as combinations of binary-digital atomic elements explicitly on the model of distinctive features theory. The lexical item "bachelor", on this basis, would be expressed as [+ Human], [+ Male], [- Married].

Supporters of this approach view the vowels and consonants recognised by speakers of a particular language or [[dialect]] at a particular time as cultural entities of little scientific interest. From a natural science standpoint, the units which matter are those common to ''Homo sapiens'' by virtue of biological nature. By combining the atomic elements or "features" with which all humans are innately equipped, anyone may in principle generate the entire range of vowels and consonants to be found in any of the world's languages, whether past, present or future. The distinctive features are in this sense atomic components of a universal language.

{|class="wikitable"
|+ Voicing contrast in English fricatives
! Articulation
! Voiceless
! Voiced
|-
|Pronounced with the lower lip against the teeth:
|{{IPA|[f]}} ('''''f'''an'')
|{{IPA|[v]}} ('''''v'''an'')
|-
|Pronounced with the tongue against the teeth:
|{{IPA|[θ]}} ''('''th'''in, '''th'''igh)''
|{{IPA|[ð]}} ''('''th'''en, '''th'''y)''
|-
|Pronounced with the tongue near the gums:
|{{IPA|[s]}} ('''''s'''ip'')
|{{IPA|[z]}} ('''''z'''ip'')
|-
|Pronounced with the tongue bunched up:
|{{IPA|[ʃ]}} ''(pre'''ss'''ure)''
|{{IPA|[ʒ]}} ''(plea'''s'''ure)''
|}

====Criticism====
In recent years, the notion of an innate "universal grammar" underlying phonological variation has been called into question. The most comprehensive [[monograph]] ever written about speech sounds, ''[[The Sounds of the World's Languages]],'' by [[Peter Ladefoged]] and [[Ian Maddieson]],<ref name=":2"/> found virtually no basis for the postulation of some small number of fixed, discrete, universal phonetic features. Examining 305 languages, for example, they encountered vowels that were positioned basically everywhere along the articulatory and acoustic continuum. Ladefoged concluded that phonological features are not determined by human nature: "Phonological features are best regarded as artifacts that linguists have devised in order to describe linguistic systems".<ref>{{cite journal|last=Ladefoged|first=P.|date=2006|title=Features and Parameters for Different Purposes|url=http://www.linguistics.ucla.edu/people/ladefoge/PLfeaturesParameters.pdf|journal=Working Papers in Phonetics|volume=104|pages=1–13}}</ref>

===Self-organisation theory===
[[Image:Sort sol ved Ørnsø 2007.jpg|right|thumb|Birds flocking, an example of [[Biological organisation|self-organization in biology]]]]

[[Self-organization|Self-organisation]] characterises systems where macroscopic structures are spontaneously formed out of local interactions between the many components of the system.<ref name="Oudeyer 2006">{{Cite book  | last1 = Oudeyer | first1 = Pierre-Yves | title = Self-organization in the evolution of speech | date = 2006 | publisher = Oxford University Press | location = Oxford University Press; New York | isbn = 978-0-19-928915-8 | oclc = 65203001 }}</ref> In self-organised systems, global organisational properties are not to be found at the local level. In colloquial terms, self-organisation is roughly captured by the idea of "bottom-up" (as opposed to "top-down") organisation. Examples of self-organised systems range from ice crystals to galaxy spirals in the inorganic world.
[[Image:TermiteMound.jpg|thumb|upright|left|A termite mound (Macrotermitinae) in the Okavango Delta just outside [[Maun, Botswana]]]]

According to many phoneticians, the sounds of language arrange and re-arrange themselves through self-organisation.<ref name="Oudeyer 2006" /><ref>Lindblom, B., MacNeilage, P., and Studdert-Kennedy, M. 1984. Self-organizing processes and the explanation of language universals. In M. Butterworth, B. Comrie and Ö Dahl (eds), ''Explanations for language universals.'' Berlin: Walter de Gruyter and Co., pp. 181-203.</ref><ref>de Boer, B. 2005b. Self-organization in language. In C. Hemelrijk (ed.), ''Self-organisation and evolution of social systems.'' Cambridge: Cambridge University Press, 123–139.</ref> Speech sounds have both perceptual (how one hears them) and articulatory (how one produces them) properties, all with continuous values. Speakers tend to minimise effort, favouring ease of articulation over clarity. Listeners do the opposite, favouring sounds that are easy to distinguish even if difficult to pronounce. Since speakers and listeners are constantly switching roles, the syllable systems actually found in the world's languages turn out to be a compromise between acoustic distinctiveness on the one hand, and articulatory ease on the other.

[[Agent-based model|Agent-based computer models]] take the perspective of self-organisation at the level of the speech community or population. The two main paradigms are (1) the iterated learning model and (2) the language game model. Iterated learning focuses on transmission from generation to generation, typically with just one agent in each generation.<ref name="Hurford 2000">{{Cite book|last1= Hurford|first1= J.R.|chapter= Social transmission favours linguistic generalization|editor1= Chris Knight |editor2=Michael Studdert-Kennedy |editor3=James R Hurford|title= The Evolutionary emergence of language: social function and the origins of linguistic form | year = 2000 | publisher = Cambridge University Press | location = Cambridge; New York | isbn = 978-0-521-78157-2 | oclc = 807262339 | pages = 324–352 }}</ref> In the language game model, a whole population of agents simultaneously produce, perceive and learn language, inventing novel forms when the need arises.<ref>{{cite journal | last1 = Steels | first1 = L | year = 1995 | title = A self-organizing spatial vocabulary | journal = Artificial Life | volume = 2 | issue = 3| pages = 319–332 | doi=10.1162/artl.1995.2.319| pmid = 8925502 | hdl = 10261/127969 | hdl-access = free }}</ref><ref>Steels, L. and Vogt, P. 1997. [http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.111.1277&rep=rep1&type=pdf Grounding adaptive language games in robotic agents]. In P. Harvey and P. Husbands (eds.), ''Proceedings of the 4th European Conference on Artificial Life.'' Cambridge, Massachusetts: MIT Press, 474–482.</ref>

Several models have shown how relatively simple peer-to-peer vocal interactions, such as imitation, can spontaneously self-organise a system of sounds shared by the whole population, and different in different populations. For example, models elaborated by Berrah et al. (1996)<ref>Berrah A-R., Glotin H., Laboissière R., Bessière P., Boë L-J. 1996. From Form to Formation of Phonetic Structures: An Evolutionary Computing Pers- pective, in Proc. ICML 1996 Workshop on Evolutionary Computing and Machine Learning, pp. 23-29, Bari, Italy.</ref> and de Boer (2000),<ref>{{cite journal |last1=de Boer |first1=Bart |title=Self-organization in vowel systems |journal=Journal of Phonetics |date=October 2000 |volume=28 |issue=4 |pages=441–465 |doi=10.1006/jpho.2000.0125 }}</ref> and recently reformulated using Bayesian theory,<ref>{{cite journal |last1=Moulin-Frier |first1=C. |last2=Laurent |first2=R. |last3=Bessière |first3=P. |last4=Schwartz |first4=J. L. |last5=Diard |first5=J. |title=Adverse conditions improve distinguishability of auditory, motor, and perceptuo-motor theories of speech perception: An exploratory Bayesian modeling study |journal=Language and Cognitive Processes |date=September 2012 |volume=27 |issue=7–8 |pages=1240–1263 |doi=10.1080/01690965.2011.645313 |s2cid=55504109 |url=https://hal.archives-ouvertes.fr/hal-01059179/file/moulin-frier12.pdf }}</ref> showed how a group of individuals playing imitation games can self-organise repertoires of vowel sounds which share substantial properties with human vowel systems. For example, in de Boer's model, initially vowels are generated randomly, but agents learn from each other as they interact repeatedly over time. Agent A chooses a vowel from her repertoire and produces it, inevitably with some noise. Agent B hears this vowel and chooses the closest equivalent from her own repertoire. To check whether this truly matches the original, B produces the vowel ''she thinks she has heard'', whereupon A refers once again to her own repertoire to find the closest equivalent. If this matches the one she initially selected, the game is successful, otherwise, it has failed. "Through repeated interactions", according to de Boer, "vowel systems emerge that are very much like the ones found in human languages".<ref>de Boer, B. 2012. Self-organization and language evolution. In M. Tallerman and K. Gibson (eds), 2012. ''The Oxford Handbook of Language Evolution.'' Oxford: Oxford University Press, pp. 612-620.</ref>

In a different model, the phonetician [[Björn Lindblom]]<ref>Lindblom. B. 1986. Phonetic universals in vowel systems. In J. J. Ohala and J. J. Jaeger (eds.), ''Experimental Phonology.'' Orlando: Academic Press, pp. 13-14.</ref> was able to predict, on self-organisational grounds, the favoured choices of vowel systems ranging from three to nine vowels on the basis of a principle of optimal perceptual differentiation.

Further models studied the role of self-organisation in the origins of phonemic coding and combinatoriality, which is the existence of [[phoneme]]s and their systematic reuse to build structured syllables. [[Pierre-Yves Oudeyer]] developed models which showed that basic neural equipment for adaptive holistic vocal imitation, coupling directly motor and perceptual representations in the brain, can generate spontaneously shared combinatorial systems of vocalisations, including phonotactic patterns, in a society of babbling individuals.<ref name="Oudeyer 2006" /><ref>{{cite journal |last1=Oudeyer |first1=Pierre-Yves |title=The self-organization of speech sounds |journal=Journal of Theoretical Biology |date=April 2005 |volume=233 |issue=3 |pages=435–449 |doi=10.1016/j.jtbi.2004.10.025 |pmid=15652151 |arxiv=cs/0502086 |bibcode=2005JThBi.233..435O |s2cid=3252482 }}</ref> These models also characterised how morphological and physiological innate constraints can interact with these self-organised mechanisms to account for both the formation of statistical regularities and diversity in vocalisation systems.

===Gestural theory===
The gestural theory states that speech was a relatively late development, evolving by degrees from a system that was originally gestural. Human ancestors were unable to control their vocalisation at the time when gestures were used to communicate; however, as they slowly began to control their vocalisations, spoken language began to evolve.

Three types of evidence support this theory:
# Gestural language and vocal language depend on similar neural systems. The regions on the [[Cerebral cortex|cortex]] that are responsible for mouth and hand movements border each other.
# Nonhuman [[primates]] minimise vocal signals in favour of manual, facial and other visible gestures in order to express simple concepts and communicative intentions in the wild. Some of these gestures resemble those of humans, such as the "begging posture", with the hands stretched out, which humans share with chimpanzees.<ref>Premack, David & Premack, Ann James. ''The Mind of an Ape'', {{ISBN|0-393-01581-5}}.</ref>
#[[Mirror neuron|Mirror Neurons]]{{Elaborate|date=June 2022}}

Research has found strong support for the idea that spoken language and signing depend on similar neural structures. Patients who used sign language, and who suffered from a left-[[cerebral hemisphere|hemisphere]] [[lesion]], showed the same disorders with their sign language as vocal patients did with their oral language.<ref>{{Cite book|title=Neuromotor Mechanisms in Human Communication |author=Kimura, Doreen |year=1993 |publisher=Oxford University Press |location=Oxford |isbn=978-0-19-505492-7}}</ref> Other researchers found that the same left-hemisphere brain regions were active during sign language as during the use of vocal or written language.<ref>{{Cite journal|title=A Critical Period for Right Hemisphere Recruitment in American Sign Language Processing |author=Newman, A. J.|year=2002 |journal=Nature Neuroscience |volume=5 |pages=76–80 |doi=10.1038/nn775 |pmid=11753419 |issue=1|s2cid=2745545|display-authors=etal}}</ref>

Humans spontaneously use hand and facial gestures when formulating ideas to be conveyed in speech.<ref>McNeill, D. 1992. ''Hand and mind.'' Chicago, IL: University of Chicago Press.</ref><ref>McNeill, D. (ed.) 2000. ''Language and gesture.'' Cambridge: Cambridge University Press.</ref> There are also, of course, many [[sign languages]] in existence, commonly associated with [[deaf]] communities; as noted above, these are equal in complexity, sophistication, and expressive power, to any oral language. The main difference is that the "phonemes" are produced on the outside of the body, articulated with hands, body, and facial expression, rather than inside the body articulated with tongue, teeth, lips, and breathing.

Many psychologists and scientists have looked into the mirror system in the brain to answer this theory as well as other behavioural theories. Evidence to support mirror neurons as a factor in the evolution of speech includes mirror neurons in primates, the success of teaching apes to communicate gesturally, and pointing/gesturing to teach young children language. Fogassi and Ferrari (2014){{Citation needed|date=June 2022|reason=Put note citation in as well}} monitored motor cortex activity in monkeys, specifically area F5 in the Broca’s area, where mirror neurons are located. They observed changes in electrical activity in this area when the monkey executed or observed different hand actions performed by someone else. Broca’s area is a region in the frontal lobe responsible for language production and processing. The discovery of mirror neurons in this region, which fire when an action is done or observed specifically with the hand, strongly supports the belief that communication was once accomplished with gestures. The same is true when teaching young children language. When one points at a specific object or location, mirror neurons in the child fire as though they were doing the action, which results in long-term learning<ref>{{Cite web|url=https://blogs.ntu.edu.sg/hg3040-2014-7/?page_id=192|title=Gestural Theory {{!}} Gestures, Speech and Sign Language in Language Evolution|website=blogs.ntu.edu.sg|access-date=2019-03-25}}</ref>

====Criticism====

Critics note that for mammals in general, sound turns out to be the best medium in which to encode information for transmission over distances at speed. Given the probability that this applied also to early humans, it is hard to see why they should have abandoned this efficient method in favour of more costly and cumbersome systems of visual gesturing – only to return to sound at a later stage.<ref>MacNeilage, P. 1998. Evolution of the mechanism of language output: comparative neurobiology of vocal and manual communication. In J. R. Hurford, M. Studdert Kennedy and C. Knight (eds), ''Approaches to the Evolution of Language.'' Cambridge: Cambridge University Press, pp. 222 41.</ref>

By way of explanation, it has been proposed that at a relatively late stage in human evolution, hands became so much in demand for making and using tools that the competing demands of manual gesturing became a hindrance. The transition to spoken language is said to have occurred only at that point.<ref>Corballis, M. C. 2002. Did language evolve from manual gestures? In A. Wray (ed.), ''The Transition to Language.'' Oxford: Oxford University Press, pp. 161-179.</ref> Since humans throughout evolution have been making and using tools, however, most scholars remain unconvinced by this argument. (For a different approach to this issue – one setting out from considerations of signal reliability and trust – see "from pantomime to speech" below).

==Timeline of speech evolution==
{{Human timeline}}
Little is known about the timing of language's emergence in the human species. Unlike writing, speech leaves no material trace, making it archaeologically invisible. Lacking direct linguistic evidence, specialists in human origins have resorted to the study of anatomical features and genes arguably associated with speech production. Whilst such studies may provide information as to whether pre-modern ''Homo'' species had speech ''capacities'', it is still unknown whether they actually spoke. Whilst they may have communicated vocally, the anatomical and genetic data lack the resolution necessary to differentiate proto-language from speech.

Using statistical methods to estimate the time required to achieve the current spread and diversity in modern languages today, [[Johanna Nichols]]&nbsp;– a linguist at the University of California, Berkeley&nbsp;– argued in 1998 that vocal languages must have begun diversifying at least 100,000 years ago.<ref>Johanna Nichols, 1998. The origin and dispersal of languages: Linguistic evidence. In Nina Jablonski and Leslie C. Aiello, eds., ''The Origin and Diversification of Language,''  pp. 127-70. (Memoirs of the California Academy of Sciences, 24.) San Francisco: California Academy of Sciences.</ref>

In 2012, anthropologists Charles Perreault and Sarah Mathew used phonemic diversity to suggest a date consistent with this.<ref>{{cite journal | last1 = Perreault | first1 = C. | last2 = Mathew | first2 = S. | year = 2012 | title = Dating the origin of language using phonemic diversity | journal = PLOS ONE | volume = 7 | issue = 4| page = e35289 | doi = 10.1371/journal.pone.0035289 | pmid = 22558135 | pmc = 3338724 | bibcode = 2012PLoSO...735289P | doi-access = free }}</ref> "Phonemic diversity" denotes the number of perceptually distinct units of sound&nbsp;– consonants, vowels and tones&nbsp;– in a language. The current worldwide pattern of phonemic diversity potentially contains the statistical signal of the expansion of modern ''Homo sapiens'' out of Africa, beginning around 60-70 thousand years ago. Some scholars argue that phonemic diversity evolves slowly and can be used as a clock to calculate how long the oldest African languages would have to have been around in order to accumulate the number of phonemes they possess today. As human populations left Africa and expanded into the rest of the world, they underwent a series of bottlenecks&nbsp;– points at which only a very small population survived to colonise a new continent or region. Allegedly such a population crash led to a corresponding reduction in genetic, phenotypic and phonemic diversity. [[African languages]] today have some of the largest phonemic inventories in the world, whilst the smallest inventories are found in South America and Oceania, some of the last regions of the globe to be colonised. For example, [[Rotokas language|Rotokas]], a language of New Guinea, and [[Pirahã language|Pirahã]], spoken in South America, both have just 11 phonemes,<ref>Maddieson, I. 1984. ''Patterns of Sounds.'' Cambridge: Cambridge University Press.</ref><ref>{{cite journal | last1 = Maddieson | first1 = I. | last2 = Precoda | first2 = K. | year = 1990 | title = Updating UPSID | journal = UCLA Working Papers in Phonetics | volume = 74 | pages = 104–111 }}</ref> whilst [[ǃKung languages|!Xun]], a language spoken in Southern Africa has 141 phonemes.
The authors use a natural experiment&nbsp;– the colonization of mainland Southeast Asia on the one hand, the long-isolated [[Andaman Islands]] on the other&nbsp;– to estimate the rate at which phonemic diversity increases through time. Using this rate, they estimate that the world's languages date back to the [[Middle Stone Age]] in Africa, sometime between 350 thousand and 150 thousand years ago. This corresponds to the speciation event which gave rise to ''Homo sapiens''.

These and similar studies have however been criticised by linguists who argue that they are based on a flawed analogy between genes and phonemes, since phonemes are frequently transferred laterally between languages unlike genes, and on a flawed sampling of the world's languages, since both Oceania and the Americas also contain languages with very high numbers of phonemes, and Africa contains languages with very few. They argue that the actual distribution of phonemic diversity in the world reflects recent language contact and not deep language history - since it is well demonstrated that languages can lose or gain many phonemes over very short periods. In other words, there is no valid linguistic reason to expect genetic founder effects to influence phonemic diversity.<ref>{{cite journal |last1=Hunley |first1=K. |last2=Bowern |first2=C. |last3=Healy |first3=M. |title=Rejection of a serial founder effects model of genetic and linguistic coevolution |journal=Proceedings of the Royal Society B: Biological Sciences |date=1 February 2012 |volume=279 |issue=1736 |pages=2281–2288 |doi=10.1098/rspb.2011.2296 |pmc=3321699 |pmid=22298843 }}</ref><ref>{{cite journal |last1=Bowern |first1=Claire |title=Out of Africa? The logic of phoneme inventories and founder effects |journal=Linguistic Typology |date=January 2011 |volume=15 |issue=2 |doi=10.1515/lity.2011.015 |s2cid=120276963 |hdl=1885/28291 |hdl-access=free }}</ref>


==See also==
{{div col|colwidth=27em}}
* [[Animal communication]]
* [[Biolinguistics]]
* [[Deception in animals]]
* [[Evolutionary anthropology]]
* [[Essay on the Origin of Languages]]
* [[Historical linguistics]]
* [[Human evolution]]
* [[Language acquisition]]
* [[Linguistic anthropology]]
* [[Linguistic universals]]
* [[Neurobiological origins of language]]
* [[Origins of society]]
* [[Origin of language]]
* [[Physical anthropology]]
* [[Proto-language]]
* [[Proto-Human language]]
* [[Recent African origin of modern humans]]
* [[Signalling theory]]
* [[Sociocultural evolution]]
* [[Symbolic culture]]
* [[Universal grammar]]
{{div col end}}

== Notes ==
{{Reflist|colwidth=30em}}

== Further reading ==
{{refbegin|30em}}
* Bickerton, D. 2009. ''Adam's Tongue.'' New York: Hill and Wang.
* Botha, R. and C. Knight (eds) 2009. ''The Prehistory of Language.'' Oxford: Oxford University Press.
* Botha, R. and C. Knight (eds) 2009. ''The Cradle of Language.'' Oxford: Oxford University Press.
* Burling, R. 2005. ''The Talking Ape. How language evolved.'' Oxford: Oxford University Press.
* Christiansen, M. and S. Kirby (eds), 2003. ''Language Evolution.'' Oxford: Oxford University Press.
* [[Michael Corballis|Corballis]], M. C., 2002. ''From Hand to Mouth: The Origins of Language.'' Princeton and Oxford: Princeton University Press.
* Deacon, T. W., 1997. ''The Symbolic Species: The Co-evolution of Language and the Brain.'' New York: W.W. Norton.
* de Boer. 2001. "The Origins of Vowels Systems", Oxford University Press.
* de Grolier, E. (ed.), 1983. ''The Origin and Evolution of Language.'' Paris: Harwood Academic Publishers.
* Deutscher, G. 2005. ''The Unfolding of Language. The evolution of mankind's greatest invention.'' London: Random House.
* Dor, D., C. Knight and J. Lewis (eds), 2014. ''The Social Origins of Language.'' Oxford: Oxford University Press.
* Dunbar, R. I. M. 1996. ''Grooming, Gossip and the Evolution of Language.'' London: Faber and Faber.
* {{Cite book  | last1 = Dunbar | first1 = R. I. M. | last2 = Knight | first2 = Chris | last3 = Power | first3 = Camilla. | title = The evolution of culture : an interdisciplinary view | year = 1999 | publisher = Edinburgh University Press | location = Edinburgh | isbn = 978-0-7486-1076-1 | oclc = 807340111 }}
* Fitch, W. T. 2010. ''The Evolution of Language.'' Cambridge: Cambridge University Press.
* Harnad, S. R., H. D. Steklis and J. Lancaster (eds), 1976. ''Origins and Evolution of Language and Speech.'' New York: Annals of the New York Academy of Sciences.
* Hrdy,  S. B. 2009. ''Mothers and others. The evolutionary origins of mutual understanding.'' London and Cambridge, Massachusetts: Belknap Press of Harvard University Press.
* Hurford, J. R. 2007. ''The Origins of Meaning. Language in the light of evolution.'' Oxford: Oxford University Press.
* {{Cite book  | last1 = Hurford | first1 = James R. | last2 = Studdert-Kennedy | first2 = Michael. | last3 = Knight | first3 = Chris | title = Approaches to the evolution of language : social and cognitive bases | year = 1998 | publisher = Cambridge University Press | location = Cambridge, UK ; New York | isbn = 978-0-521-63964-4 | oclc = 37742390}}
* Kenneally, C. 2007. ''The First Word. The search for the origins of language.'' New York: Viking.
* Lenneberg, E. H. 1967. ''Biological Foundations of Language.'' New York: Wiley.
* Leroi-Gourhan, A. 1993. ''Gesture and Speech.'' Trans. A. Bostock Berger. Cambridge, Massachusetts: MIT Press.
* {{Cite book | last1 = Lieberman | first1 = Philip. | title = Uniquely human : the evolution of speech, thought, and selfless behavior | year = 1991 | publisher = Harvard University Press | location = Cambridge, Massachusetts | isbn = 978-0-674-92182-5 | oclc = 21764294 | url = https://archive.org/details/uniquelyhumanevo00lieb }}
* {{Cite book  | last1 = Lieberman | first1 = Philip. | title = Toward an evolutionary biology of language | year = 2006 | publisher = Belknap Press of Harvard University Press | location = Cambridge, Massachusetts | isbn = 978-0-674-02184-6 | oclc = 62766735 }}
* Logan, Robert K. 2007. "The Extended Mind: The Emergence of Language, the Human Mind and Culture. Toronto: University of Toronto Press.
* MacNeilage, P. 2008. ''The Origin of Speech.'' Oxford: Oxford University Press.
* Maynard Smith, J. and D. Harper 2003. ''Animal Signals.'' Oxford: Oxford University Press.
* Oudeyer, P-Y. (2006) "Self-Organization in the Evolution of Speech", Oxford University Press.
* Tallerman, M. and K. Gibson (eds), 2012. ''The Oxford Handbook of Language Evolution.'' Oxford: Oxford University Press.
* Tomasello, M. 2008. ''Origins of Human Communication.'' Cambridge, Massachusetts: MIT Press.
* Zahavi, A. and A. Zahavi 1997. ''The Handicap Principle. A missing piece in Darwin's puzzle.'' New York and Oxford: Oxford University Press.
{{refend}}

==External links==
* [http://homes.chass.utoronto.ca/~danhall/phonetics/sammy.html Interactive sagittal section]
* [http://people.exeter.ac.uk/bosthaus/Lecture/hockett1.htm Design features of speech] {{Webarchive|url=https://web.archive.org/web/20120722050927/http://people.exeter.ac.uk/bosthaus/Lecture/hockett1.htm |date=2012-07-22 }}
* [http://www.cog.brown.edu/people/lieberman/pdfFiles/Lieberman%20P.%202007.%20The%20evolution%20of%20human%20speech,%20Its%20anatom.pdf Evolution of speech (anatomical and neural bases).] {{Webarchive|url=https://web.archive.org/web/20140611203314/http://www.cog.brown.edu/people/lieberman/pdfFiles/Lieberman%20P.%202007.%20The%20evolution%20of%20human%20speech,%20Its%20anatom.pdf |date=2014-06-11 }}
* [http://www.radicalanthropologygroup.org/old/class_text_089.pdf Ritual and the origins of language.]{{Dead link|date=December 2022 |bot=InternetArchiveBot |fix-attempted=yes }}
* [http://www.radicalanthropologygroup.org/old/class_text_070.pdf Decoding Chomsky]{{Dead link|date=December 2022 |bot=InternetArchiveBot |fix-attempted=yes }}

{{Evolutionary psychology}}
{{Human Evolution}}

[[Category:Language]]