Language evolution and complexity considerations: The no half-Merge fallacy

Abstract

Recently, prominent theoretical linguists have argued for an explicit scenario for the evolution of the human language capacity on the basis of its computational properties. Concretely, the simplicity of a minimalist formulation of the operation Merge, which allows humans to recursively compute hierarchical relations in language, has been used to promote a sudden-emergence, single-mutation scenario. In support of this view, Merge is said to be either fully present or fully absent: one cannot have half-Merge. On this basis, it is inferred that the emergence of our fully fledged language capacity had to be sudden. Thus, proponents of this view draw a parallelism between the formal complexity of the operation at the computational level and the number of evolutionary steps it must imply. Here, we examine this argument in detail and show that the jump from the atomicity of Merge to a single-mutation scenario is not valid and therefore cannot be used as justification for a theory of language evolution along those lines.

Vocal learning: Beyond the continuum

“…However, such approaches prevent comparative work almost by definition. As far as we can tell, reductionist views of the language phenotype have not been fruitful and have led to implausible scenarios for the evolution of language [39,88]. The case of vocal learning is not as extreme because virtually any definition of it yields more than one species with the trait, therefore allowing for some comparative work (although according to the VLC, humans are the only high-end vocal learners).…”

“…The other problem is that if a goal (or even the main goal) of comparative work is to derive information about the evolution of traits and species, we cannot expect a single aspect (e.g., a single genetic change or a single brain connection) to offer a realistic picture of how the trait evolved [39]. Even if the empirical evidence established that only vocal learning species in any one sense consistently have a certain brain connection and vice versa, evolutionary aspirations would still require a more complex explanation.…”

All or nothing: No half-Merge and the evolution of syntax

“…In their Essay [1], Martins and Boeckx (MB) take issue with our proposals about the evolution of language in our book Why Only Us (WOU) [2] and offer an alternative. As we will show, their critique is misguided and their alternative untenable.…”

“…First, in [1], MB do not question our assumption that the core properties of language are based on the combinatorial operation Merge, with the standard definition of its basic operation: binary set formation [1,2]. Our disagreement has to do with evolution of this operation.…”

“…In [2], we devote nearly an entire chapter to this topic, “Triangles in the Brain,” pp. 109–166, in which we discuss both these topics, including analysis of the general architecture for such an operation and the empirical evidence for various computer science–based algorithms grounding it, and how these might crucially affect language use, all with an eye towards Marr’s distinctions about the distinct levels of algorithm and implementation that [1] also stresses. (See, e.g., [2] pp.…”