A paper by Gell-Mann & Ruhlen in PNAS this week conducts a phylogenetic analysis of word order in languages and concludes that SOV is the most likely ancestor language word order. The main conclusions from the analysis are:
(i) The word order in the ancestral language was SOV.
(ii) Except for cases of diffusion, the direction of syntactic change, when it occurs, has been for the most part SOV > SVO and, beyond that, SVO > VSO/VOS with a subsequent reversion to SVO occurring occasionally. Reversion to SOV occurs only through diffusion.
(iii) Diffusion, although important, is not the dominant process in the evolution of word order.
(iv) The two extremely rare word orders (OVS and OSV) derive directly from SOV.
This analysis agrees with Luke Maurtis' work on function and Uniform Information Density (blogged about here).
This week we had a talk by visiting PhD student Luke Maurits about basic word order. The distributions of basic word orders around the world (Subject-Verb-Object, Subject-Object-Verb etc. ) has been the focus of much attention. The overwhelming majority of languages have SOV and SVO orders, with fewer having VSO and very small numbers having OVS and OSV. In order of frequency, this is:
(SOV, SVO) > VSO > (VOS, OVS) > OSV
A standard approach has been to assume that this ordering reflects an ordering of functionality: Somehow, SOV order is more functional or efficient or intuitive than OSV. However, Maurits points out that the literature on diachronic change opposes this view. Languages often change from SOV to VSO or SVO over time, but rarely the other way around (see diagram below).