Degeneracy. The evolutionary advantage of the violation of isomorphism

In Construction Grammar approaches, language is often conceived of as a network of form-meaning pairings. In a Saussurean conception of the construction as a sign, the ideal situation would be one in which there is an isomorphic relation between form and function, meaning that homonymy and synonymy are potentially problematic (Haiman 1980; McMahon 1994: 85). Recent studies have argued that this ideal isomorphic organization of the constructicon is constantly violated: diachronically, we find that (i) similarity in form begets similarity in function and vice versa (De Smet 2010, Fonteyn 2016), (ii) superficial (i.e. etymologically unwarranted) similarity may affect the formal realization of neighbouring constructions (Pijpops & Van de Velde 2016) and may lead to diachronic merger of distinct lineages (Van de Velde & Van der Horst 2013; Van de Velde et al. 2013), and (iii) forms with partially overlapping functions may attract each other leading to full overlap in functions (De Smet et al., forthc.). It is findings (i) and (iii) that lead to synonymy and (ii) to polysemy. In sum, constructions constantly interact on a formal as well as a functional-semantic level. This multitude of complex interactions causes that forms and functions do not exhibit one-to-one, but many-to-many relationships. Such many-to-many mappings also occur in natural evolution and go under the name of ‘degeneracy’. Degeneracy is defined as the property by which structurally different elements can fulfill the same function, but at the same time are involved in other functions as well (e.g. the human body uses perspiration and widening of arteries to cool off, but the former strategy is also used in increased oxygen transport and the latter in getting toxins out of the body). In language, degeneracy means that one linguistic form can come to play a role in (many) different functions (i.e. ‘syncretism’; see also Robertson 1983; Norde 2014), but at the same time those functions can also be expressed by (many) other forms. Importantly, degeneracy is different from many-forms-to-one-meaning mapping (synonomy/redundancy) and from one-form-to-many-meanings (polysemy). Previous studies on linguistic degeneracy have argued that it enhances robustness of the signal (Van de Velde 2014; Winter 2014): synchronically, degeneracy adds redundancy to the linguistic expression, protecting the acoustic signal from interference by ambient noise, and diachronically, degeneracy makes languages flexible to sustain damage in times of syntactic change. Under a Diachronic Construction Grammar view, degeneracy is the reason why the sign system does not collapse when constructional changes occur: constructions are marked by several forms at once, each of which can be tweaked or repurposed without losing the meaning of the sign. In this talk, we will look at two cases of degeneracy, and argue that they indeed make a language robust in times of change. Our first case study deals with nominalization. We will show that the wide array of nominalization strategies in English (e.g. for you to win/you winning the award/your winning of the award/your win) do not constitute a strictly isomorphic but a degenerate system: nominalization is achieved by different formal strategies that each realize their own distinct, yet partially overlapping set of functions. When a particular strategy becomes unavailable, then, its neighboring nominalization strategies can compensate for its loss. Our second case study deals with the order of the verb in Germanic (V1 – V2 – V-final): each verb order expresses a range of functions (e.g. V1 for questions, subordinated clauses and imperatives), and the functions they express are robustly encoded by other forms as well (e.g. rising intonation, conjunctions, subject omission, respectively). 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