Emergence of new communication systems

Among human populations, language contact is the norm, and it often leads not only to language change (cf. "Innovation (language change and variation)") but also to the birth of new languages that arise in either spoken or signed form. In spoken language, two or more languages may come into direct contact via trade, colonization, importation of a foreign labor force, or some combination of these factors. Often in such situations, one of the populations coming into contact represents a sociopolitically and economically dominant culture known as the "superstrate," and the subordinate or subjgated culture or cultures are known as the "substrate". Typically in these situations, the substrate population vastly outnumbers the superstrate population, and may be drawn from different language groups. It is also often the case that the superstrate culture will deny education to the substrate population. In an attempt to arrive at a common mode of communication, vocabulary is drawn mostly from the superstrate language with few to none of its structural properties. The result is referred to as a "pidgin", which has a lexicon adequate for everyday communicative purposes but little to no structural regularity. Over a few generations, a pidgin can begin to develop its own structural regularities on the way to becoming a fully linguistic system known as a "creole". Creole languages have been studied extensively because they tend to exhibit very similar structural properties, even though they arise in different parts of the globe from completely different superstrate and substrate languages. One hypothesis among many proposed has been that children born into pidgin-speaking populations add structural complexity and regularity to the language system they are exposed to, thus driving the development of a pidgin toward a full-fledged creole language. The situations that give rise to new sign languages are more happenstance. Of particular note among several documented cases of new sign languages are situations in Nicaragua and among a Bedouin community in Israel. In Central America, deafness is not hereditary, but typically caused by viral infections. Prior to the Sandinista revolution in Nicaragua, children who lost their hearing were neither schooled nor exposed to any form of sign language. Under the Sandinista program of universal education, including special education, deaf individuals who had previously lived apart from one another were brought together for the first time in centralized educational settings. Instruction was given in lip-reading and speaking, but students communicated gesturally with each other on their own, using gestural systems they had developed at home, or from interacting with others. Over time, a full-blown sign language known as "Nicaraguan Sign Language" emerged whose properties have been studied extensively. On the basis of studies comparing cohorts of students by decade in the deaf schools, it appears to be the case that it is indeed the younger members of the community who provide systematicity and add structural complexity to the language. This is also consistent with recent experimental research showing that when presented with an inconsistent artificial language system in which one pattern occurs 60% of the time and an alternative pattern 40% of the time, adult learners reproduce the probabilities of the input in their output (i.e., 60/40), while children tend to regularize the majority pattern and use it 90% of the time. The situation of the Bedouin community in Israel is in many ways different from that in Nicaragua: the typical cause of deafness is not childhood disease but hereditary deafness. This means that deafness can appear more than once, indeed several times within an extended family. The frequency of deafness across families has led to wide use of the sign language among hearing as well as deaf members of the community. The signing community has existed over three generations, with conventionalization of lexicon and sentence structure. Younger signers in the Bedouin community produce longer utterances and sign at a faster rate than older generations of signers, which is one of several markers of language emergence and change over time. There is no known parallel in animal communication of two or more systems merging to produce an emergent system that differs from either/any of the original systems. There is a documented case of one humpback vocalization "dialect" supplanting another when an Indian Ocean population came into contact on the eastern coast of Australia with a Pacific population. There was however no evidence of merger of hybridization, let alone a new system emerging that differed from both of these  original systems. There appears to be some evidence for a new system arising completely de novo. It is well-known that when raised in isolation, male songbirds produce only a divergent, often reduced version of the full-fledged adult male species-specific song. It has recently been shown that when the only input to zebra finches raised in isolation is the divergent song of such a male, the new generation imitates it, but also adds features typical of the song sung by zebra finches in the wild. The same happens when the song of a male of this new generation is provided as input to the next generation, and so on, such that within three or four generations, the song of isolates reverts to the speciec-specific song sung in the wild.