In preparation: Journal for Evolutionary Linguistics 1(1). 2010 Can Evolutionary Linguistics Become a Science? Luc Steels∗1;2 1AI Laboratory, Vrije Universiteit Brussels, Pleinlaan 2 1050 Brussels, Belgium 2Sony Computer Science Laboratory, 6 Rue Amyot, 75005 Paris, France Email: Luc Steels∗- [email protected]; ∗Corresponding author Abstract The paper introduces a methodology for developing evolutionary explanations for features of human natural languages. The methodology is inspired by Evolutionary Biology but maps the Darwinian selectionist framework to the cognitive and linguistic level. Point of departure is a particular language system found in human languages, such as tense and aspect marking or the expression of spatial relations. To remain empirically grounded, the language system is studied by means of a concrete realisation in a particular human language, for example case marking in Icelandic or subordinate clauses in German. The methodology suggests to first survey what kind of conceptual, lexical and grammatical structures we find in the chosen human language and to reconstruct the production and comprehension processes that can handle them. It proposes next to investigate the role of the language system in linguistic communication by designing a language game where it is beneficial. Then the learning, alignment, and expansion strategies that individuals need to acquire and self-organize a language system are reconstructed, and the processes by which these strategies could originate by the recruitment of cognitive mechanisms are identified. To explain why a language strategy has become adopted by a population, the final stage in the methodology studies the selectionist advantage of the language system by showing how it helps to increase communicative success, provide enough expressive power, and minimise cognitive effort. The paper gives a concrete example of this methodology, and discusses the general selectionist framework underlying it. 1 Introduction [7, 12, 13, 18, 21, 45, 49, 52]. There are now regular `Evolution of Language' conferences that bring these How did human natural languages originate and why diverse fields together in an interdisciplinary dialog, and how do they continue to evolve? This fas- starting from 1996 [46], and there is a growing liter- cinating question has received a growing amount ature with monographs, collections of articles, and of interest over the past decade from many dis- publications in a wide range of journals. Out of all ciplines. We see contributions from anthropology, these activities, a new field of research is beginning archeology, historical linguistics, neurobiology, cog- to crystalise that does not approach the study of lan- nitive psychology, evolutionary biology, genetics, ar- guage evolution from the perspective of an existing tificial intelligence, and complex systems research 1 discipline but sees this research topic as its central like genetic drift, punctuated equilibria, exaptation, core. I believe this field is best called `Evolutionary epigenesis, genetic hitch-hiking, the Baldwin effect, Linguistics'. The goal of this paper is to reflect on transposons, and so on. However, recent research on the methodology that could most profitably be used speciation has seemed to confirm rather than further to develop this field and I will suggest that Evolu- question the role of natural selection in the origins tionary Biology can act as a source of inspiration. of species [51], and so I will mainly restrict the dis- Evolutionary Biology is one of the best developed cussion to that. areas of contemporary science and it acts as a glue We need a comparable general framework for that pulls together all other biological disciplines: Evolutionary Linguistics. One approach might be ethology, ecology, molecular biology, population dy- to apply the Darwinian proposal literally, in other namics, development, and genetics. As Dobzhansky words, to consider language to be a biological adap- famously put it: \Nothing in biology makes sense tation which has evolved through genetic evolution except in the light of evolution." [28] Evolutionary and natural selection. This can only be the case Linguistics could possibly play a similar assembling if the following conditions are met: (i) There are role for the study of language and meaning, which dedicated phenotypic traits for language. It is usu- is currently fragmented into different subdisciplines ally argued that this is a highly specialized modular that hardly interact with each other. `language organ' in the brain. (ii) There is a crit- Evolutionary Linguistics draws necessarily on ical role of `language genes' for building these spe- many existing linguistic subdisciplines: Historical cialized brain structures. And (iii) greater linguistic linguistics produces data and insight in the actual aptitude leads to higher biological fitness, so that evolution of human languages. Cognitive linguis- the language genes spread and remain in the gene tics and construction grammar contribute studies pool. Some researchers are pursuing this biological on the rich semantics and pragmatics underlying hypothesis [6, 55, 57, 63, 90], but it is not the only human languages and how they are grammatically possibility. expressed. Computational linguistics provides con- It could also be that language evolution is a spe- crete models of syntactic parsing, production and cial case of cultural evolution based on the recruit- language learning. Developmental linguistics docu- ment of cognitive mechanisms that are also useful ments the pathways by which children or second lan- in other domains [20, 36, 53, 60, 79, 81, 93]. In that guage learners acquire language. And neurolinguis- case the possible analogy between biological evolu- tics makes concrete proposals about the neural basis tion and language evolution is at a more abstract of language, including the way the many cognitive level. The explanatory targets are not biological functions needed for language might have evolved. phenotypic traits but language features. We still ex- But Evolutionary Linguistics wants to go be- pect to see heredity, variation, and selection to am- yond these efforts by developing explanations of how plify those variants that are more adapted to a par- and why certain linguistic phenomena could have ticular set of challenges, but heredity will be based evolved, not only in terms of empirical findings of on memory and learning rather than genetic trans- actual human language evolution but also in terms mission. Variation will come from the unavoidable of formal models and systematic experiments. Thus divergence in linguistic behavior due to the different it helps to move linguistics from a descriptive en- development histories of the members of a popula- deavour to an explanatory science, from describing tion and performance deviations in actual discourse. features of human languages or their evolution to And selection will not be natural selection (i.e. based explaining why they are there. on biological fitness in an ecosystem) but linguistic The first reason why Evolutionary Biology has selection that amplifies the use of conceptualisations been so successful is because Darwin established a and linguistic constructions that lead to higher com- clear general framework to explain adaptation and municative success, greater expressive power, and speciation and to develop concrete evolutionary ex- less cognitive effort. In the rest of this paper, I will planations for phenotypic features of living beings, focus on this socio-cultural perspective on language such the color patterns of the wings of butterflies evolution, as I believe it has so far yielded the most or organs like the liver. There have been many re- explanatory power. finements and enhancements of this framework, sug- The epistemological status of Darwinian evolu- gesting supplementary causes or factors in evolution, tionary theory is quite different from other natural 2 science theories such as Newtonian mechanics, in the 2 Language systems and Language sense that it provides a framework for explaining Strategies phenomena but the details still need to be worked The first useful concept of evolutionary theory, as out for each specific case. For example, it does not currently conceptualized, is the distinction between directly explain why a particular species of butter- genotype and phenotype. A genotype consists of a flies has certain color patterns on the wings. It only network of genes that builds a concrete organism, suggests how we can go about finding such an expla- a phenotype, through a very complex developmental nation. In contrast, the equations of mechanics can process that typically integrates epigenetic factors be applied to any falling body by simply plugging in and environmental influences. The genotype also in- the relevant quantities and parameters. fluences the further operation, adaptation, and re- The explanatory framework that we can hope for pair of the phenotype as its life unfolds. in Evolutionary Linguistics might be more similar to An organism finds itself in a particular ecosys- that of Evolutionary Biology than that of physics, tem, a portion of the world that is populated by in the sense that there might not be a single cog- other species and has certain physical characteristics nitive mechanism, like recursion, or a single most like temperature or humidity. The organism gets a important function of early language, like hunting chance to play the game of life: It moves around in or courtship, or a single set of