Language: A Uniquely Human Capacity
When considering the differences between humans and other species, there are several fields where a distinction is macroscopically observable. There are some things that only humans seem to be able to do: create and use artefacts and technologies, sequence the genome, project and fly aeroplanes. No other species is able to manipulate matters and objects to the same degree: chimpanzees, which are among the closest relatives to humans, for example, have the ability to, in a very limited form, use sticks to reach food (Köhler 1925). If we shift to a more symbolic level, Homo sapiens is the only species that has developed writing systems. What about language? Common sense would suggest that human language is not entirely different from communication systems documented in other species like primates or bees. But the reality is that human language (hereafter simply 'language') has very little in common with these systems. So, we face two fundamental problems: to explain what is the main function of language, and how humans developed it.
Language and Communication
The vulgata about language is that it works primarily as a means of communication. Language seems to fit perfectly our daily need to share information, ask questions, and talk about the world. Linguistic data, however, suggests that this conclusion may be wrong. Language shows an optimal design: it converts thoughts into words which i) are articulated and perceived through our motor sense system (though not necessarily: think about sign languages) and ii) carry a global meaning. But do these features completely satisfy communication needs? Not at all. Languages exhibit phenomena that go against optimal communication requirements. One of these phenomena is called agreement and is exemplified by the following sentences in English and Italian:
(a) The cat that the dog chased ran away.
(b) I cani del vicino abbaiano sempre ("The neighbour's dogs always bark").
Reading these sentences, the speaker of both languages intuitively knows that: i) in the sentence (a) the verb chased agrees (=grammatically pairs) with the dog, while the verb ran away agrees with the cat and ii) in the sentence (b) the verb abbaiano (3rd person plural of the verb abbaiare 'to bark') agrees with the subject of the sentence i cani ('the dogs') and not to the closer noun vicino ('neighbour'). Both examples (and there is no attested language which differs in this respect, cfr. Moro 2015, p. 211) indicate that language exhibits restriction to the relationships between words in a sentence; in other words, languages show structural dependency. There is no way to justify this feature in terms of communication efficiency, quite the contrary: structural dependency is computationally costly and communicatively redundant. Why do we not just simply put the subject and its relative predicate near so that we are not forced to parse the structure of the entire sentence in order to understand what our interlocutor is talking about?
Another example of how language is not functional for efficient communication is represented by the phenomenon of sentence ambiguity. Consider the following English sentence:
(c) I saw some kids in the park using a telescope.
This sentence is interpretable in two totally different ways: one of which is that I used a telescope to see the kids in the park; the other is that I saw the kids in the park while they were using a telescope. Again, why would we need such ambiguity in a verbal interchange? Animal systems show totally different features, since a) their signals are reactions to external stimuli (e.g. a monkey produces a specific kind of sound in case of danger and a different one when indicating food) and, being this is their primary evolutionary function, b) they are communicatively adequate to this scope not showing traces of agreement operations or syntactic ambiguity. It has been shown how language differs with respect to b). What about a)? Well, language is evidently an intentional behaviour which may refer to external stimulus, but it is not caused by it.
Can Primates Learn a Language?
A serious effort to demonstrate there is no substantial cognitive gap between human language and animal communication systems was made between the 70s and 80s by psychologists and anthropologists. In 1979 a team of researchers led by Herbert S. Terrace breed a chimpanzee from an early age and named him 'Neam Chimpsky', after the notorious American linguist Noam Chomsky (b. 1928) who had repeatedly denied that monkeys could manipulate languages (Terrace et al. 1979). The team attempted to teach Neam the American Language Sign (ALS), given the anatomic impossibility for monkeys to produce human sounds like vowels and consonants. Since ALS is perfectly symmetric to verbal language in terms of computational complexity and structural dependency, if Neam could succeed in mastering it, the experiment would have shown quite convincingly that humans and primates are not different at all in terms of cognitive capacities related to language competence. But the results were quite disappointing for the researchers. Neam Chimpsky could memorize and use, in everyday communication with the researchers, a quite remarkable quantity of words - he acquired around 120 words in a short time -, but his sentences showed serious limitations in terms of structure. Neam very rarely used more than two words in a sentence and in no case did the insertion of extra words give rise to a systematic syntax like that exhibited by humans: Neam could express the desire to eat a banana by saying indifferently eat banana or banana eat. This is different to how human languages work. Any child acquiring English, for example, shows, if considered at a certain level of their developmental process, the capacity to manipulate word order to create different kinds of structures: we can imagine that, in infant talk, sit daddy chair and daddy sit chair have two totally different interpretations, the first meaning '(I/you/he-she/... sit(s) on daddy's chair)' while the second meaning 'daddy sits on the chair'). The learning process of Neam continued, showing progressively that children of his same age had developed a largely more refined capacity in a series of syntactic domains: children's sentences were longer on average, up to 8 times longer when both Neam and the children reached 52 months, and Neam did not show any sensibility to basic pragmatic requirements of language interchange such as respecting each other's turn in a conversation (Moro 2015, p. 85-86).
We saw how language differs from other systems of communication used by other animals. Now, let us consider how language evolved. Since writing appeared relatively late in human history - it appeared almost simultaneously in Asia, Africa and America between 3500 e il 3300 B.C. (Martin 1988) - and when humans had fully developed the language faculty (LF), we have very few hints on what language looked like when it emerged. Nevertheless, some elements may help us. Archaeological evidence suggests that our first ancestors appeared in Africa around 200,000 years ago (a further precise periodization is not possible yet in current research, cfr. Hublin et al. 2017). Rests included in this span of time show anatomic characteristics shared by all members of Homo sapiens and differences in those of other close relatives like Pan troglodytes (common chimpanzee), the main ones being erect posture and a larger brain. These characteristics are a relevant clue which suggests that humans' cognitive capacities did not emerge much later (maybe between 50,000 and 100,000 years ago): since humans did not undergo further anatomic transformations, their brain circuits were already compatible with higher cognitive capacities like language. Indeed, If so, we must suppose that language didn't really evolve in the classical sense of the term. Quite differently, it seems it appeared abruptly and in a sort of complete shape (Tattersal 2012, p. XI).
There is no doubt that LF is part of that set of abilities referred to as superior cognitive capacities, but how did Homo Sapiens develop language? There is a serious debate on this topic. For a long time, and even before evolution was an accepted theory in the scientific community, biology held the principle that natura non facit saltus, a Latin expression introduced by Carl Linnaeus in 1751 which literally means 'nature does not make jumps'. This formula was used to deny that sudden changes could happen in natural history. Darwin's theory seemed to reinforce this principle, indicating that, although nature drives constant processes of transformation, these changes follow a slow and somewhat irregular track. According to Jacques Monod, changes in an evolutionary perspective are gradual and determined by the random variation of the genetic code; for these reasons, the appearance of a new species requires a huge amount of time and is an effect of totally random genetic mutations; these mutations, of course, must be beneficial in order to be perpetrated in next generations (Monod, 1970). This view is totally compatible with the principle mentioned earlier and supports the idea that language is no more than the refinement of the basic communicative abilities of primates. As we saw, there are problems with this idea: historically, language seems more of a sudden and overwhelming jump rather than a slow and gradual change. And even some biologists, as we will see, are sceptical that language evolved out of communication needs. At the same time, no serious linguist, psychologist or biologist would deny the fact that language is a product of evolution. It seems more of a problem of compatibility. Is there a possible solution? There are at least three options.
Considering that Homo sapiens and other primates like chimpanzees share more than 98% of their genetic heritage, biologist François Jacob claims the real key to explaining humans' cognitive capacities, such as language, is the variation of a few genes through the process referred to as 'gene regulation'; this process is responsible for significant variations even when comparing two strictly related species (Jacob, 1981). Another biologist, Stephen Jay Gould, explains language as the result of a process called 'exaptation': an organ originally used for a function may shift to new, different, scopes (Gould, 1991). Possibly, language originated from an exaptation process, which involved different organs (lungs, vocal tract, brain areas) and their related functions (breath, mastication, memory, abstract thinking). Put in these terms, language is nothing but a parasitic function which exploits pre-existing systems. A third possible explanation is the one proposed by linguist Noam Chomsky, who sees LF as the result of a sudden reframing of the brain circuit, which let the first humans apply the core operations of language. These operations, referred to as (External) Merge and Move (or Internal Merge), are behind the very basic phenomena shown by human syntax, like putting words together and moving elements in a sentence to make it passive or interrogative, like in: Who has Lisa gone to the cinema with [who]? - Lisa has gone to the cinema with Diego (Hauser, Chomsky, Fitch 2002; Chomsky 2016).
At the end of this historical, biological, and linguistic journey, it is fair to claim that language is a uniquely human capacity with no comparable attested parallel in the rest of the animal kingdom. It is not yet entirely clear when exactly it was shaped the way we now know it and how. At the present stage of research, language seems to offer a list of challenges not just to linguistics, but also to other fields, like biology, psychology and cognitive neurosciences. Language is a complex and somewhat confusing phenomenon: we know very little about it despite the fact we use it constantly and with no effort. It seems that the true key to new exciting findings in the field of language is to consider simple phenomena - the ones that we constantly produce while speaking our own language, like grammatical agreement - and show how they are complex and important to explain how the brain/mind works.
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Figure 1. Charles Robert Darwin. A copy made by John Collier (1850-1934) in 1883 of his 1881 portrait of Charles Darwin. John Collier, Public domain, via Wikimedia Commons: https://commons.wikimedia.org/wiki/File:Charles_Robert_Darwin_by_John_Collier.jpg
Figure 2. Sue Savage-Rumbaugh (L), Kanzi (R), and his sister Panbinisha (C) working at the portable "keyboard" (2006). William H. Calvin, PhD, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons: https://commons.wikimedia.org/wiki/File:Bonobos_Panbanisha_%26_Kanzi_with_Sue_Savage-Rumbaugh,_2006.jpg
Figure 3. Nim signing with Laura-Ann Petitto, Susan Kiklin, via NBC News: https://www.nbcnews.com/science/cosmic-log/nim-little-chimp-couldnt-flna6c10403000