Linguists agree that there are no existing primitive languages, and all modern human populations speak languages of comparable complexity. While existing languages differ in the size of and subjects covered in their lexicons, all possess the grammar and syntax needed, and can invent, translate, or borrow the vocabulary necessary to express the full range of their speakers' concepts. All humans possess similar linguistic abilities, and no child is born with a biological predisposition favoring any one language or type of language.
Human language had emerged by the transition to behavioral modernity some 50,000 years ago at the latest (Upper Paleolithic). A common assumption is that behavioral modernity and the emergence of language coincide and are dependent on one another, while others would push back the origin of language to some 200,000 years ago, the time of the appearance of archaic Homo sapiens (Middle Paleolithic), or even into the Lower Paleolithic, to some 500,000 years ago. This question significantly depends on the view taken of the communicative skills of Homo neanderthalensis. In either case, a lengthy stage of pre-language, intermediate between Great ape language and fully developed human language, needs to be assumed.
In the wild, the communication of vervet monkeys has been the most studied. They are known to make up to ten different vocalizations. Many of these are used to warn other members of the troupe about approaching predators, and include a "leopard call", a "snake call", and an "eagle call". Each alarm triggers a different defensive strategy. Scientists were able to elicit predictable responses from the monkeys using loudspeakers and prerecorded sounds. Other vocalizations 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.
There is considerable speculation about the language capabilities of ancient hominids. Some scholars believe the advent of hominid bipedalism around 3.5 million years ago would have brought changes to the human skull, allowing for a more L-shaped vocal tract. The shape of the tract and a larynx positioned relatively low in the neck are necessary prerequisites for many of the sounds humans make, particularly vowels. Other scholars believe that, based on the position of the larynx, not even the Neanderthals had the anatomy necessary to produce the full range of sounds modern humans make. Still another view considers the lowering of the larynx irrelevant to the development of speech.
An absolute proto-language, as defined by linguist Derek Bickerton, is a primitive form of communication lacking:
That is, a stage in the evolution of language somewhere between Great ape language and fully developed modern human language.
The term Hmmmmm has been proposed for the pre-linguistic system of communication used by archaic Homo (beginning with Homo ergaster and reaching the highest sophistification with Homo neanderthalensis. Hmmmmm is an acronym for holistic (non-compositional), manipulative (utterances are commands or suggestions, not descriptive statements), multi-modal (acoustic as well as gestural and mimetic), musical and memetic.
Anatomical features such as the L-shaped vocal tract have been continuously evolving as opposed to appearing suddenly. Even though archaic humans used crude stone technology, it was still more advanced than that of chimpanzees or gorillas. Hence it is most likely that archaic humans possessed some form of communication intermediate between that of modern humans and that of other primates.
However, although Neanderthals may have been anatomically able to speak, Richard G. Klein in 2004 doubted that they possessed a fully modern language. They largely base their doubts on the fossil record of archaic humans and their stone tool kit. For 2 million years following the emergence of Homo habilis, the stone tool technology of hominids changed very little. Richard G. Klein, who has worked extensively on ancient stone tools, describes the crude stone tool kit of archaic humans as impossible to break down into categories based on their function, and reports that Neanderthals seem to have had little concern for the final form of their tools. Klein argues that the Neanderthal brain may have not reached the level of complexity required for modern speech, even if the physical apparatus for speech production was well-developed. The issue of the Neanderthal's level of cultural and technological sophistication remains a controversial one.
The greatest step in language evolution would have been the progression from primitive, pidgin-like communication to a creole-like language with all the grammar and syntax of modern languages. Many scholars believe that this step could only have been accomplished with some biological change to the brain, such as a mutation. It has been suggested that a gene such as FOXP2 may have undergone a mutation allowing humans to communicate. Evidence suggests that this change took place somewhere in East Africa around 100,000 to 50,000 years ago, which rapidly brought about significant changes that are apparent in the fossil record. There is still some debate as to whether language developed gradually over thousands of years or whether it appeared suddenly.
According to the Out of Africa hypothesis, around 50,000 years ago a group of humans left Africa and proceeded to colonize the rest of the world, including Australia and the Americas, which had never been populated by archaic hominids. Some scientists believe that Homo sapiens did not leave Africa before that, because they had not yet attained modern cognition and language, and consequently lacked the skills or the numbers required to migrate. However, given the fact that Homo erectus managed to leave the continent much earlier (without extensive use of language, sophisticated tools, nor anatomical modernity), the reasons why anatomically modern humans remained in Africa likely had more to do with climatic conditions.
All humans alive today are descended from Mitochondrial Eve, a woman estimated to have lived in Africa some 150,000 years ago. This raises the possibility that the Proto-World language could date to approximately that period. There are also claims of a population bottleneck, notably the Toba catastrophe theory which postulates human population at one point some 70,000 years ago was as low as 15,000 or even 2,000 individuals. If it indeed transpired, such a bottleneck would be an excellent candidate for the date of Proto-World, which also illustrates the fact that Proto-World would not necessarily date to the first emergence of language.
Some proponents of a Proto-World hypothesis, such as Merritt Ruhlen, have attempted to reconstruct the Proto-World language. However, most mainstream linguists reject these attempts and the methods they use (such as mass lexical comparison) for a number of reasons.
Two types of evidence support this theory.
Research found strong support for the idea that verbal language and sign language depend on similar neural structures. Patients who used sign language, and who suffered from a left-hemisphere lesion, showed the same disorders with their sign language as vocal patients did with their spoken language. Other researchers found that the same left-hemisphere brain regions were active during sign language as during the use of vocal or written language.
The important question for gestural theories is why there was a shift to vocalization. There are three likely explanations:
Humans still use hand and facial gestures when they speak, especially when people meet who have no language in common. Deaf people also use languages composed entirely of signs.
If contact is maintained between the groups speaking the pidgin for long periods of time, the pidgins may become more complex over many generations. If the children of one generation adopt the pidgin as their native language it develops into a creole language, which becomes fixed and acquires a more complex grammar, with fixed phonology, syntax, morphology, and syntactic embedding. The syntax and morphology of such languages may often have local innovations not obviously derived from any of the parent languages.
Studies of creole languages around the world have suggested that they display remarkable similarities in grammar and are developed uniformly from pidgins in a single generation. These similarities are apparent even when creoles do not share any common language origins. In addition creoles share similarities despite being developed in isolation from each other. syntactic similarities include Subject Verb Object word order. Even when creoles are derived from languages with a different word order they often develop the SVO word order. Creoles tend to have similar usage patterns for definite and indefinite articles, and similar movement rules for phrase structures even when the parent languages do not.
Another issue that is often cited as support for the Universal grammar theory is the recent development of Nicaraguan Sign Language. Beginning in 1979, the recently installed Nicaraguan government initiated the country's first widespread effort to educate deaf children. Prior to this there was no deaf community in the country. A center for special education established a program initially attended by 50 young deaf children. By 1983 the center had 400 students. The center did not have access to teaching facilities of any of the sign languages that are used around the world; consequently, the children were not taught any sign language. The language program instead emphasized spoken Spanish and lipreading, and the use of signs by teachers limited to fingerspelling (using simple signs to sign the alphabet). The program achieved little success, with most students failing to grasp the concept of Spanish words.
The first children who arrived at the center came with only a few crude gestural signs developed within their own families. However, when the children were placed together for the first time they began to build on one another's signs. As more younger children joined the language became more complex. The children's teachers, who were having limited success at communicating with their students, watched in awe as the kids began communicating amongst themselves.
Later the Nicaraguan government would solicit help from Judy Kegl, an American sign-language expert at Northeastern University. As Kegl and other researchers began to analyze the language, they noticed that the young children had taken the pidgin-like form of the older children to a higher level of complexity, with verb agreement and other conventions of grammar.
Religions and ethnic mythologies often provide explanations for the origin and development of language. Most mythologies do not credit humans with the invention of language, but know of a language of the gods (or, language of God), predating human language. Mystical languages used to communicate with animals or spirits, such as the language of the birds, are also common, and were of particular interest during the Renaissance.
One of the best known examples in the West is the Tower of Babel passage from Genesis in the Bible or Torah. The passage, common to all Abrahamic faiths, tells of God punishing man for the tower's construction by means of the confusion of tongues (Genesis 11:1–9). Local variations of this passage are found to have followed Christian missionaries on their journeys across the world, although the extent to how much of the tradition existed prior to the arrival of the missionaries is still discussed.