Origin of language
Grammaticalisation theory

" Grammaticalisation " is a continuous historical process in which free-standing words develop into grammatical appendages, while these in turn become ever more specialised and grammatical. An initially "incorrect" usage, in becoming accepted, leads to unforeseen consequences, triggering knock-on effects and extended sequences of change. Paradoxically, grammar evolves because, in the final analysis, humans care less about grammatical niceties than about making themselves understood. If this is how grammar evolves today, according to this school of thought, similar principles at work can be legitimately inferred among distant human ancestors, when grammar itself was first being established.

In order to reconstruct the evolutionary transition from early language to languages with complex grammars, it is necessary to know which hypothetical sequences are plausible and which are not. In order to convey abstract ideas, the first recourse of speakers is to fall back on immediately recognizable concrete imagery, very often deploying metaphors rooted in shared bodily experience. A familiar example is the use of concrete terms such as "belly" or "back" to convey abstract meanings such as "inside" or "behind". Equally metaphorical is the strategy of representing temporal patterns on the model of spatial ones. For example, English speakers might say "It is going to rain", modelled on "I am going to London." This can be abbreviated colloquially to "It's gonna rain." Even when in a hurry, English speakers do not say "I'm gonna London"—the contraction is restricted to the job of specifying tense. From such examples it can be seen why grammaticalisation is consistently unidirectional—from concrete to abstract meaning, not the other way around.

Grammaticalisation theorists picture early language as simple, perhaps consisting only of nouns. Even under that extreme theoretical assumption, however, it is difficult to imagine what would realistically have prevented people from using, say, "spear" as if it were a verb ("Spear that pig!"). People might have used their nouns as verbs or their verbs as nouns as occasion demanded. In short, while a noun-only language might seem theoretically possible, grammaticalisation theory indicates that it cannot have remained fixed in that state for any length of time.

Creativity drives grammatical change. This presupposes a certain attitude on the part of listeners. Instead of punishing deviations from accepted usage, listeners must prioritise imaginative mind-reading. Imaginative creativity—emitting a leopard alarm when no leopard was present, for example—is not the kind of behaviour which, say, vervet monkeys would appreciate or reward. Creativity and reliability are incompatible demands; for "Machiavellian" primates as for animals generally, the overriding pressure is to demonstrate reliability. If humans escape these constraints, it is because in their case, listeners are primarily interested in mental states.

To focus on mental states is to accept fictions—inhabitants of the imagination—as potentially informative and interesting. An example is metaphor: a metaphor is, literally, a false statement. In Romeo and Juliet, Romeo declares "Juliet is the sun!". Juliet is a woman, not a ball of plasma in the sky, but human listeners are not (or not usually) pedants insistent on point-by-point factual accuracy. They want to know what the speaker has in mind. Grammaticalisation is essentially based on metaphor. To outlaw its use would be to stop grammar from evolving and, by the same token, to exclude all possibility of expressing abstract thought.

A criticism of all this is that while grammaticalisation theory might explain language change today, it does not satisfactorily address the really difficult challenge—explaining the initial transition from primate-style communication to language as it is known today. Rather, the theory assumes that language already exists. As Bernd Heine and Tania Kuteva acknowledge: "Grammaticalisation requires a linguistic system that is used regularly and frequently within a community of speakers and is passed on from one group of speakers to another". Outside modern humans, such conditions do not prevail.
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