Evolution within a language: environmental differences contribute to divergence of dialect groups

Abstract

BackgroundThe processes leading to the diversity of over 7000 present-day languages have been the subject of scholarly interest for centuries. Several factors have been suggested to contribute to the spatial segregation of speaker populations and the subsequent linguistic divergence. However, their formal testing and the quantification of their relative roles is still missing. We focussed here on the early stages of the linguistic divergence process, that is, the divergence of dialects, with a special focus on the ecological settings of the speaker populations. We adopted conceptual and statistical approaches from biological microevolution and parallelled intra-lingual variation with genetic variation within a species. We modelled the roles of geographical distance, differences in environmental and cultural conditions and in administrative history on linguistic divergence at two different levels: between municipal dialects (cf. in biology, between individuals) and between dialect groups (cf. in biology, between populations).ResultsWe found that geographical distance and administrative history were important in separating municipal dialects. However, environmental and cultural differences contributed markedly to the divergence of dialect groups. In biology, increase in genetic differences between populations together with environmental differences may suggest genetic differentiation of populations through adaptation to the local environment. However, our interpretation of this result is not that language itself adapts to the environment. Instead, it is based on Homo sapiens being affected by its environment, and its capability to adapt culturally to various environmental conditions. The differences in cultural adaptations arising from environmental heterogeneity could have acted as nonphysical barriers and limited the contacts and communication between groups. As a result, linguistic differentiation may emerge over time in those speaker populations which are, at least partially, separated.ConclusionsGiven that the dialects of isolated speaker populations may eventually evolve into different languages, our result suggests that cultural adaptation to local environment and the associated isolation of speaker populations have contributed to the emergence of the global patterns of linguistic diversity.Electronic supplementary materialThe online version of this article (10.1186/s12862-018-1238-6) contains supplementary material, which is available to authorized users.

Geographical and social isolation drive the evolution of Austronesian languages

“…We found no association between geographical isolation and within-community conflict in our sample ( χ 2 = 52.66, df = 44, p = 0.17; S2 Fig ). Therefore it is unlikely that geographical isolation promotes differentiation either by increasing social group cohesion [ 33 ] or intensifying within-group conflict over resources [ 58 ]. In summary, we argue that geographical isolation may have contributed to differentiation among Austronesian languages mostly by preventing the random loss of existing lexical items, despite also hindering the ability of novel lexical innovations to emerge and be utilised [ 38 , 59 ], rather than by affecting the internal social dynamics of isolated groups.…”

“…For example, population density, local interconnectedness and migrations were claimed to play a key role in cumulative cultural evolution by facilitating the emergence, diffusion and survival of linguistic innovations [18,21,[27][28][29][30]. In contrast, social, cultural and political settings [31,32] might also promote social group cohesion and the sharing of linguistic features within groups, which would reduce rates of linguistic differentiation [33].…”

Uralic typology in the light of a new comprehensive dataset

“…Thus, they fit especially well to linguistic typological data. Admixture models have been applied in linguistics to study language families (Reesink et al 2009) and dialects (Syrjänen et al 2016;Honkola et al 2018Honkola et al , 2019. The application of model-based clustering algorithms to linguistic data is discussed in depth elsewhere (Syrjänen et al 2016;Syrjänen 2021).…”

“…Kipot ja Kielet research project (2018Kielet research project ( -2020 led by Päivi Onkamo and Outi Vesakoski; several Kone Foundation projects: UraLEX (2014UraLEX ( -2016 led by Unni-Päivä Leino;SumuraSyyni (2013SumuraSyyni ( -2016 and AikaSyyni (2017AikaSyyni ( -2021 led by Outi Vesakoski: OV, TH and YJ were funded by AikaSyyni. Research was also supported by the Turku University Foundation (Terhi Honkola) as well as Collegium for Transdisciplinary Studies in Archeology, Genetics and Linguistics, University of Tartu (2018-), and partly by the Estonian Research Council (grants No.…”

Socio-cultural similarity with host population rather than ecological similarity predicts success and failure of human migrations

“…cross-cousin marriage practices may depend on a population's subsistence strategy) [ 26 ], the forms of words themselves have no fitness implications so linguistic differences are often used as neutral markers to track the diverging cultural histories of populations [ 27 ]. Using linguistic differences between municipalities in Finland, Honkola et al [ 28 ] found that diverging dialects were better predicted by ecological and cultural differences than geographical distance. This supports the view of cultural adaptation proponents who argue that cultural practices respond to challenges posed by particular environments [ 29 ].…”