Commentary: Issues of time, tone, roots and replicability

Abstract

In their article, Language evolution and climate: the case of desiccation and tone , Everett et al. (2016) conclude by suggesting that, ‘the time has come to more substantively examine the possible ecological adaptations of linguistic sound systems’. Indeed, many of us want to convincingly identify what are the causal impacts that shape the evolution of languages, whether those are at the phonological level or elsewhere. The broader question is how do we substantively examine not only ecological, but also extralinguistic environmental factors—be it biological, cognitive, cultural, physical, or social elements (De Busser 2015)—that potentially trigger or influence adaptations of linguistic structure? This challenge is in the spotlight of public interest,1 academic criticism and potential prestige. It is also set against the backdrop of increasingly large datasets and powerful statistical software, which makes it easy to find (spurious) correlations (cf. Roberts and Winters 2013). Although studies are moving away from mere observed correlations and toward causal theories, many methodological considerations remain. In this commentary, I mention issues of timescale, deep-rooted phonology and tone in regard to Everett et al.'s (henceforth the authors) proposal, and I discuss broader issues of data, statistics, and replicability of results moving forward. How do external real-world factors influence or trigger linguistic adaptations? It is a bold, but not new assertion: ‘articulation of linguistic sounds is ecologically adaptive’ (Everett et al. 2016). But how much time is needed for linguistic adaptations to occur?2 To give an idea of timescale, consider that over millions of years there has been remarkable variation in the morphology and function of the vertebrate tongue, appearing to be related to evolutionary events and environmental conditions respective of habitat (Iwasaki 2002). But for the studies of interest here, let us assume that ecological adaptiveness (of sound or other linguistic subsystems) must …