Self-domesticated ape theory
According to a study investigating the song differences between white-rumped Munias and its domesticated counterpart (Bengalese finch), the wild munias use a highly stereotyped song, whereas the domesticated ones sing a highly unconstrained song. Considering that song syntactical complexity is subject to female preference in the Bengalese finch, it is likely that maternal resource allocation strategies play a role in song evolution.[9] In the field of bird vocalization, brains capable of producing only an innate song have very simple neural pathways: the primary forebrain motor center, called the robust nucleus of arcopallium (RA), connects to midbrain vocal outputs which in turn project to brainstem motor nuclei. By contrast, in brains capable of learning songs, the RA receives input from numerous additional forebrain regions, including those involved in learning and social experience. Control over song generation has become less constrained, more distributed, and more flexible.
When compared with other primates, whose communication system is restricted to a highly stereotypic repertoire of hoots and calls, humans have very few prespecified vocalizations, extant examples being laughter and sobbing. Moreover, these remaining innate vocalizations are generated by restricted neuronal pathways, whereas language is generated by a highly distributed system involving numerous regions of the human brain.
A salient feature of language is that while language competency is inherited, the languages themselves are transmitted via culture. Also transmitted via culture are understandings, such as technological ways of doing things, that are framed as language-based explanations. Hence one would expect a robust co-evolutionary trajectory between language competency and culture: proto-humans capable of the first, and presumably rudimentary, versions of protolanguage would have better access to cultural understandings, and cultural understandings, conveyed in protolanguages that children's brains could readily learn, were more likely to be transmitted, thereby conferring the benefits accrued.
Hence proto-humans indubitably engaged in, and continue to engage in, what is called niche construction, creating cultural niches that provide understandings key to survival, and undergoing evolutionary changes that optimize their ability to flourish in such niches. Selection pressures that operated to sustain instincts important for survival in prior niches would be expected to relax as humans became increasingly dependent on their self-created cultural niches, while any innovations that facilitated cultural adaptation—in this case, innovations in language competency—would be expected to spread.
One useful way to think about human evolution is that we are self-domesticated apes. Just as domestication relaxed selection for stereotypic songs in the finches—mate choice was supplanted by choices made by the aesthetic sensibilities of bird breeders and their customers—so might our cultural domestication have relaxed selection on many of our primate behavioral traits, allowing old pathways to degenerate and reconfigure. Given the highly indeterminate way that mammalian brains develop—they basically construct themselves "bottom up," with one set of neuronal interactions setting the stage for the next round of interactions—degraded pathways would tend to seek out and find new opportunities for synaptic hookups. Such inherited de-differentiations of brain pathways might have contributed to the functional complexity that characterizes human language. And, as exemplified by the finches, such de-differentiations can occur in very rapid timeframes.[10][11]
[edit] Synergetic approach
The Azerbaijan Linguistic School works on the belief that speech does not precede language and is not the only instrument for language performance. Language can exist without speech, and nonverbal means can play the role of shell (medium) for language. Humans developed the verbal language form because other channels of communication are not so extensive or comfortable. Here natural selection favours the verbal channel. Despite the dominance of the visual channel in everyday human relations with the outside world, it is insufficiently reliable for individual security. Human vision apprehends at any given moment only a quarter of the visible environment, and is usable for only half of the time (i.e., during wakefulness). The efficiency of the visual channel is also limited by various adverse conditions such as smoke, fog, or any other obstacles.
The auditory canal activity is available for 24 hours in the range of 360 degrees in space. The only barrier for sound propagation is strong noise, which is a very atypical occurrence. Furthermore, in order to communicate with a person visually it is necessary that this person sees the communicator. On the other hand, the auditory canal is open around the clock for perception of information from all sides, from anyone, and without any special settings. All this contributed to the human verbal (oral) form of language development.
It is hypothesized that the mechanism of modern sophisticated and overly complicated human languages development is identical to the writing evolutionary mechanism, and has evolved through the following four stages:
- Stage I: Phoneme = sentence (pictographic language);
- Stage II: Phoneme = word or phrase (ideographic language);
- Stage III: Phoneme = syllable (syllabic language);
- Stage IV: Phoneme = sound (phonetic language).
That is, some utterance first substituted (designated) a whole sentence, then — only a part of the sentence, and then — part of the word.[12][13][14][15]
