Editing Origin of language (section)

=== Primate communication ===
Field primatologists can give useful insights into [[great ape]] communication in the wild.<ref name="Arcadi2000" /> One notable finding is that nonhuman primates, including the other great apes, produce calls that are graded, as opposed to categorically differentiated, with listeners striving to evaluate subtle gradations in signallers' emotional and bodily states. Nonhuman apes seemingly find it extremely difficult to produce vocalisations in the absence of the corresponding emotional states.<ref name="Goodall1986" /> In captivity, nonhuman apes have been taught rudimentary forms of sign language or have been persuaded to use [[lexigrams]]—symbols that do not graphically resemble the corresponding words—on computer keyboards. Some nonhuman apes, such as [[Kanzi]], have been able to learn and use hundreds of lexigrams.<ref>{{Cite book |last1=Savage-Rumbaugh |first1=E. Sue |title=Kanzi: the ape at the brink of the human mind |last2=Lewin |first2=Roger. |publisher=Wiley |year=1994 |isbn=978-0-471-58591-6 |location=New York}}</ref><ref>{{Cite book |last1=Savage-Rumbaugh |first1=E. Sue |url=https://archive.org/details/apeslanguagehuma00sava |title=Apes, language, and the human mind |last2=Shanker |first2=Stuart. |last3=Taylor |first3=Talbot J. |publisher=Oxford University Press |year=1998 |isbn=978-0-19-510986-3 |location=New York}}</ref>

The [[Broca's area|Broca's]] and [[Wernicke's area]]s in the primate brain are responsible for controlling the muscles of the face, tongue, mouth, and larynx, as well as recognizing sounds. Primates are known to make "vocal calls", and these calls are generated by circuits in the [[brainstem]] and [[limbic system]].<ref>Freeman, Scott; Jon C. Herron., ''Evolutionary Analysis'' (4th ed.), Pearson Education, Inc. (2007), {{ISBN|0-13-227584-8}} pages 789–90</ref>

In the wild, the communication of [[vervet monkey]]s has been the most extensively studied.<ref name="Diamond1992" /> They are known to make up to ten different vocalizations. Many of these are used to warn other members of the group about approaching predators. They include a "leopard call", a "snake call", and an "eagle call".<ref>{{Cite journal |last1=Seyfarth |first1=Robert M. |last2=Cheney |first2=Dorothy L. |last3=Marler |first3=Peter |year=1980 |title=Vervet monkey alarm calls: Semantic communication in a free-ranging primate |journal=Animal Behaviour |volume=28 |issue=4 |pages=1070–1094 |doi=10.1016/S0003-3472(80)80097-2 |s2cid=53165940}}</ref> Each call triggers a different defensive strategy in the monkeys who hear the call and scientists were able to elicit predictable responses from the monkeys using loudspeakers and prerecorded sounds. Other vocalisations may be used for identification. If an infant monkey calls, its mother turns toward it, but other vervet mothers turn instead toward that infant's mother to see what she will do.<ref>{{Cite journal |last1=Arnold |first1=Kate |last2=Zuberbühler |first2=Klaus |year=2006 |title=Language evolution: Semantic combinations in primate calls |journal=Nature |volume=441 |issue=7091 |page=303 |bibcode=2006Natur.441..303A |doi=10.1038/441303a |pmid=16710411 |s2cid=4413635 |doi-access=free}}</ref><ref>{{Cite news |last=Wade, Nicholas |date=23 May 2006 |title=Nigerian Monkeys Drop Hints on Language Origin |url=https://www.nytimes.com/2006/05/23/science/23lang.html |access-date=9 September 2007 |work=[[The New York Times]]}}</ref>

Similarly, researchers have demonstrated that chimpanzees (in captivity) use different "words" in reference to different foods. They recorded vocalisations that chimps made in reference, for example, to grapes, and then other chimps pointed at pictures of grapes when they heard the recorded sound.<ref>{{Cite thesis |last=Gibbons |first=Christopher M. |title=The referentiality of chimpanzee vocal signaling: behavioral and acoustic analysis of food barks |publisher=[[Ohio State University]] |url=http://rave.ohiolink.edu/etdc/view?acc_num=osu1173219994 |year=2007}}</ref><ref>{{Cite journal |last1=Slocombe |first1=Katie E. |last2=Zuberbühler |first2=Klaus |year=2005 |title=Functionally Referential Communication in a Chimpanzee |url=http://doc.rero.ch/record/278602/files/Slocombe_K.-Functionally_refererential_20170201172432-HV.pdf |journal=Current Biology |volume=15 |issue=19 |pages=1779–1784 |bibcode=2005CBio...15.1779S |doi=10.1016/j.cub.2005.08.068 |pmid=16213827 |s2cid=6774592}}</ref>