RT Journal Article
SR Electronic
T1 Evolutionary Dynamics Do Not Motivate a Single-Mutant Theory of Human Language
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 517029
DO 10.1101/517029
A1 Bart de Boer
A1 Bill Thompson
A1 Andrea Ravignani
A1 Cedric Boeckx
YR 2019
UL http://biorxiv.org/content/early/2019/01/10/517029.abstract
AB Abstract One of the most controversial hypotheses in cognitive science is the Chomskyan evolutionary conjecture that language arose instantaneously in our species as the result of a single staggeringly fortuitous mutation. Here we analyze the evolutionary dynamics implied by this hypothesis, which has never been formalized. The theory supposes the emergence and fixation of a single mutant (capable of the syntactic operation Merge) during a narrow historical window as a result of frequency-independent selection under a huge fitness advantage in a population of an effective size that is standardly assumed to have been no larger than ~15 000 early humans. We examine this proposal by combining diffusion analysis and extreme value theory to derive a probabilistic formulation of its dynamics. Perhaps counter-intuitively, a macro-mutation is much more unlikely a priori than multiple mutations with smaller fitness effects, yet both hypotheses predict fixation with high conditional probability. The consequences of this asymmetry have not been accounted for previously. Our results diffuse any suggestion that evolutionary reasoning provides an independent rationale for the controversial single-mutant theory of language.Significance statement In recent years, Chomsky and colleagues have sought support for their minimalist theory of the language faculty from evolutionary considerations. They have argued for a spontaneous emergence of a mutation conferring an advantage for thought independent of communication. Here for the first time a formalization of this view is offered, and contrasted with a more gradual evolutionary scenario. The outcome of our analysis argues against the Chomskyan view.