This post is a guest contribution by James Winters, the proprietor of Replicated Typo, a group blog about language and evolution. James holds a MSc in the evolution of language and cognition from the University of Edinburgh, and is contemplating going on for a doctorate. If you have an idea for a post, and you’d like to contribute to Nothing in Biology Makes Sense, e-mail Jeremy to inquire.
Just over 140 years ago, Charles Darwin famously discussed the striking parallels between the forces that govern language change and the evolutionary processes underlying species formation:
“The formation of different languages and of distinct species, and the proofs that both have been developed through a gradual process, are curiously parallel… We find in distinct languages striking homologies due to community of descent, and analogies due to a similar process of formation… We see variability in every tongue, and new words are continually cropping up; but as there is a limit to the powers of memory, single words, like whole languages, gradually become extinct” (Darwin, 1871: 78-79).
Darwin recognised, along with several other linguists of the period such as August Schleicher and Mikołaj Kruszewski, that language falls under the remit of evolutionary principles. Since then, there has been a renewed and growing interest in evolutionary (Croft, 2000) and ecological (Mufwene, 2000) theories of language change, with biological, cultural and linguistic forms of evolution being captured by the more general rubric of Complex Adaptive Systems. First coined by Holland (1992), CAS are a subset of nonlinear dynamical systems in that they exhibit emergent properties as a result of multiple, interconnected elements. However, it is the capacity to evolve and adapt that differentiates language and biology from these other systems, with the key concept being their ability to learn: past experiences filter through, or influence, future states of the system due to cumulative amplification dynamic (Deacon, 2010).
These perspectives have led to a cross-fertilisation of terminology, ideas and models, which allows us to shed new light on the problems facing linguists in the 21st Century. Given the growing body of evidence from how it is acquired, used and changed, a consensus is forming that language displays all the hallmarks of a CAS:
“(1) The system consists of multiple agents (the speakers in the speakers in the speech community) interacting with one another. (2) The system is adaptive, that is, speakers’ behavior is based on their past interactions, and current and past interactions together feed forward into future behavior. (3) A speaker’s behavior is the consequence of competing factors ranging from perceptual mechanics to social motivations. (4) The structures of language emerge from interrelated patterns of experience, social interaction and cognitive processes” (Beckner et al., 2009: 3 [PDF]).
Critically, this perspective allows us to place the existence of language at two inter-dependent junctures, consisting of an idiolect (the individual language user) and the communal language (the community of users). Both of these aspects are emergent: idiolects emerge from each individual’s use of their language through interactions in the speech community, and the communal language consists of these interactions between the idiolects. Rather than viewing language as belonging to a “completely homogenous speech-community” (Chomsky, 1965: 3), it is perhaps better construed as consisting of numerous speech communities, overlapping and varying across space and time. Every language is, as William Croft (2000: 92) profoundly put, “a multiplicity of codes”.
A general theory of language, then, needs to integrate perspectives from biological, social and cultural realms if we are able to cover the origins and evolution of language.
Biological Evolution of Language
An important question for evolutionary linguists is how the “structures and processes needed for language could have evolved in the course of biological evolution” (Steels, 2011: 1). One of the major shifts in thinking about language came in 1990, when Steven Pinker and Paul Bloom published their groundbreaking paper: Natural language and natural selection. In it, they argue natural selection was the central process in shaping the biological structures underpinning language. For some features, particularly the physical capacity to produce and receive multiple vocalizations, there is ample evidence for specialisation: a descended larynx, thoracic breathing, and several distinct hearing organs. Given that these features are firmly in the domain of biology, it makes intuitive sense to apply the theory of natural selection to solve the problem: humans are specially adapted to the production and reception of multiple vocalizations.
Yet Pinker and Bloom’s argument is found somewhat wanting when extended to incorporate the notion that natural selection shaped specialised mental organs, or modules, for acquiring language. First and foremost, the notion of a putative language acquisition device (commonly referred to as LAD) is not an established fact: rather, it’s derived from Noam Chomsky’s arguments from the poverty of the stimulus (POTS) and assumptions that all languages are essentially the same in structure, but differ in their sound systems and vocabularies. As such, under the stewardship of Pinker, Chomsky and others, the origin, evolution and acquisition of language is primarily seen as a biological question to be answered.
Even if this is the case, and we place most of our focus on the biological evolution of language, the notion of a domain-specific, language acquisition device is something that still divides linguists. Yet, in an ongoing debate spanning at least several decades, there is still no evidence, at least to my knowledge, for the existence of a LAD. Although, you’d be forgiven for thinking that the problem was solved many years ago, especially if you were to believe the now eighteen-year old words of Massimo Piatelli-Palmarini (1994 [PDF]):
“The extreme specificity of the language system, indeed, is a fact, not just a working hypothesis, even less a heuristically convenient postulation. Doubting that there are language-specific, innate computational capacities today is a bit like being still dubious about the very existence of molecules, in spite of the awesome progress of molecular biology”
The rationale for thinking that we have some innate capacity for acquiring language can be delineated into a twofold argument: first, children seem adept at rapidly learning a language, even though they aren’t exposed to all of the data; and second, cognitive science told us that our brains are massively modular, or at the very least, should entail some aspect that is domain specific to language (see FLB/FLN distinction in Hauser, Chomsky & Fitch, 2002 [PDF]). Whilst it is certain that biological plays a role in the evolution of language, under a CAS perspective there still remains the question as to the relative contributions of cultural evolution.
Cultural Evolution of Language
If we accept that language is not only a conveyor of cultural information, but it is itself a socially learned and culturally transmitted system, then an individual’s linguistic knowledge is the result of observing the linguistic behaviour of others. This well attested process of language acquisition is often termed Iterated Learning, and it opens up a new avenue to investigate the design features of language: that cultural, as opposed to biological, evolution is fundamental in understanding these features.
Much of the literature regarding Iterated Learning focuses on a computational modelling approach, where “the central idea behind the ILM [Iterated Learning Model] is to model directly the way language exists and persists via two forms of representation” (Kirby & Hurford, 2002: 123). These two forms consist of an I-Language (the internal representation of language as a pattern of neural connections) and an E-Language (the external representation of language as sets of utterances). This cycle of continued production and induction is used to understand how the evolution of structure emerges from non-linguistic communication systems and how language changes from one form into another.
To briefly summarise, these models contain a single agent who is taught an initial random language (consisting of mappings between meanings and signals). The output of the agent is then used to teach the next generation, and so on. After numerous generational turnovers of teachers and observers, some of these models provide an intriguing insight into the emergence of linguistic phenomena underpinning the basic structures of language, such as compositionality and regularity.
A common theme running through a wide array of these Iterated Learning studies emphasises language as being a compromise between two factors: “the biases of learners, and other constraints acting on language during their transmission.” (Smith, 2009: 697). What is perhaps fundamental to this view is encapsulated in the second constraint: that the transmission is a mediating force in the shaping of language. For instance, Kirby & Hurford (2002) show how the infinite expressivity found in languages is a result of the finite set of data presented during acquisition. With this transmission bottleneck restricting the amount of data presented, learners must generalise in order to learn the data, but not to the extent where the language is one signal for all possible meanings. Tempering maximal expressivity with generalisation provides an adequate explanation for recursive compositionality, without appealing to the need for an intricately specified Language Acquisition Device (LAD). As Zuidema (2003) succinctly put it: “the poverty of the stimulus solves the poverty of the stimulus”.
These modelling observations are backed up by experiments utilising real human learners. As Kirby notes:
“By placing the artificial language learning paradigm within a cultural transmission framework, we can observe the evolution of languages in the laboratory (Kirby, Cornish & Smith, 2008). Results from these experiments show that linguistic structure does indeed emerge from initially random systems, and furthermore that this process is non-intentional. In other words, this cultural process provides “design without a designer” just as biological evolution does”.
The consequences for offloading a large portion of the evolutionary work onto cultural systems are particularly profound in the realm of social structure.
Croft (2011 [PDF]), for instance, has argued some types of language change are only a recent phenomenon in human history. He develops several universals based on Service’s (1971) classification of bands, tribes, chiefdoms and states. First, the divergence of languages is believed to be a characteristic of all society types, and largely stems from some sort of social fissioning. Croft does note, however, that the consolidation of states might lead to less divergence, albeit dependent on its degree of political integration. In contrast, certain types of language interference – and the subsequent products of these processes – are somewhat tied to the society type. In particular, the emergence of contact and mixed languages are associated with certain society types. We see this through the development of long-distance, complex trade routes and migratory patterns found in states and, to a lesser extent, chiefdoms.
Capturing similar sentiments is Lupyan & Dale’s Linguistic Niche Hypothesis (LHN): that just as the structure of biological organisms are affected by their ecological niche, the structure of society influences the evolutionary pressures on language structure. Socio-demographic forces are thus predicted to influence language structure in three fundamental ways: (i) Community Size; (ii) Network Density and Multiplexity; (iii) Learner Bias Composition (e.g. degree of adult versus child language learning). Taken together, these forces regulate contact between individuals within a speech community, and it is this concept of interaction through which linguistic knowledge is built, maintained and changed. Societal complexity will therefore influence what an individual is exposed to, how their linguistic, social and cultural knowledge is structured, and impact upon the pressures underpinning successful acts of communication.
Languages, then, not only undergo a process of gradual drifting until they become mutually unintelligible, they also adapt in response to any salient pressures present within the interactional environment. That there are so many forces intertwined in a seemingly inextricable system is something we should view as liberating and awe inspiring, just as Darwin did in his beautifully formed paragraph about the tangled bank, in which he described how “endless forms most beautiful and most wonderful have been, and are being evolved”. So too can linguists make similar claims as they cross those curious parallels.
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