Phoneme Inventory Size and Demography

It’s long since been established that demography drives evolutionary processes (see Hawks, 2008 for a good overview). Similar attempts are also being made to describe cultural (Shennan, 2000; Henrich, 2004; Richerson & Boyd, 2009) and linguistic (Nettle, 1999a; Wichmann & Homan, 2009; Vogt, 2009) processes by considering the effects of population size and other demographic variables. Even though these ideas are hardly new, until recently, there was a ceiling as to the amount of resources one person could draw upon. In linguistics, this paucity of data is being remedied through the implementation of large-scale projects, such as WALS, Ethnologue and UPSID, that bring together a vast body of linguistic fieldwork from around the world. Providing a solid direction for how this might be utilised is a recent study by Lupyan & Dale (2010). Here, the authors compare the structural properties of more than 2000 languages with three demographic variables: a language’s speaker population, its geographic spread and the number of linguistic neighbours. The salient point being that certain differences in structural features correspond to the underlying demographic conditions.

With that said, a few months ago I found myself wondering about a particular feature, the phoneme inventory size, and its potential relationship to underlying demographic conditions of a speech community. What piqued my interest was that two languages I retain a passing interest in, Kayardild and Pirahã, both contain small phonological inventories and have small speaker communities. The question being: is their a correlation between the population size of a language and its number of phonemes? Despite work suggesting at such a relationship (e.g. Trudgill, 2004), there is little in the way of empirical evidence to support such claims. Hay & Bauer (2007) perhaps represent the most comprehensive attempt at an investigation: reporting a statistical correlation between the number of speakers of a language and its phoneme inventory size.

In it, the authors provide some evidence for the claim that the more speakers a language has, the larger its phoneme inventory. Without going into the sub-divisions of vowels (e.g. separating monophthongs, extra monophtongs and diphthongs) and consonants (e.g. obstruents), as it would extend the post by about 1000 words, the vowel inventory and consonant inventory are both correlated with population size (also ruling out that language families are driving the results). As they note:

That vowel inventory and consonant inventory are both correlated with population size is quite remarkable. This is especially so because consonant inventory and vowel inventory do not correlate with one another at all in this data-set (rho=.01, p=.86). Maddieson (2005) also reports that there is no correlation between vowel and consonant inventory size in his sample of 559 languages. Despite the fact that there is no link between vowel inventory and consonant inventory size, both are significantly correlated with the size of the population of speakers.

Using their paper as a springboard, I decided to look at how other demographic factors might influence the size of the phoneme inventory, namely: population density and the degree of social interconnectedness.

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The Movius Line represents the crossing of a demographic threshold

ResearchBlogging.orgWhen examining the dispersal of Pleistocene hominins, one of the more fascinating debates concern the patterns of biological and technological evolution in East Asia and other regions of the Old World. One suggestion emerging from palaeoanthropological research places a demarcation between these two regions in the form of a geographical division known as the Movius Line. Specifically, the suggestions that initially led to the Movius Line were based on observations of differing technological patterns, namely: the lack of Acheulean handaxes and the Levallois core traditions in East Asia.

Since Hallam L. Movius’ initial proposal, the recent discovery of handaxes within East Asia have led to suggestions that the Movius Line is in fact obsolete. Suggesting this may not in fact be the case is a recent paper by Stephen Lycett & Christopher Norton, which highlights three central points coming from a growing body of research: 1) “several morphometric analyses have identified statistically significant differences between the attributes of specific biface assemblages from east and west of the Movius Line”; 2) “The number of sites from which handaxes have been recovered in East Asia tend to be geographically sparse compared with many regions west of the Movius Line”;  3) “‘handaxe’  specimens  tend only  to comprise a  small percentage of the total number of artefacts recovered, a situation that  contrasts  with  many  classic  Acheulean  sites  in  western portions of the Old World, where bifacial handaxes may dominate assemblages in large numbers”.

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Cumulative Culture Evolved to Rapidly Coordinate Novel Behaviours

ResearchBlogging.orgIn the deliberations over humanity and its perceived uniqueness, a link is frequently made between our ability to support a rich, diverse culture and the origin of complex human behaviour. Yet what is often overlooked in our view of these two, clearly connected phenomena is the thread that weaves them together: the ability to coordinate behaviour. We need only look at the products of our culture, from language to religion, to see that any variant we may deem successful is contingent on coordinating the behaviour of two or more individuals. Still, what is truly illuminating about this ability is that, far from being a uniquely human feature, the ability to coordinate behaviour is ubiquitous throughout the many organismal kingdoms.

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