The Evolution of Linguistic Diversity
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The Evolution of Linguistic Diversity Daniel Nettle Thesis submitted for the degree of PhD University College London 1996 ProQuest Number: 10044366 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. uest. ProQuest 10044366 Published by ProQuest LLC(2016). Copyright of the Dissertation is held by the Author. All rights reserved. This work is protected against unauthorized copying under Title 17, United States Code. Microform Edition © ProQuest LLC. ProQuest LLC 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106-1346 ABSTRACT This thesis examines the causes and consequences of diversity in human language. It is divided into three sections, each of which addresses a different aspect of the topic. The first section uses computer simulations to examine various mechanisms which may produce diversity in language: imperfect learning, geographical isolation, selection on the basis of social affiliation, and functional selection amongst linguistic variants. It is concluded that social and functional selection by speakers provide the main motive forces for the divergence of languages. The second section examines the factors influencing the geographical distribution of languages in the world. By far the most important is the ecological regime in which people live. Seasonal climates produce large ethnolinguistic groups because people form large networks of exchange to mitigate the subsistence risk to which they are exposed. Non-seasonal, equatorial climates such as those of Papua New Guinea and Zaire produce numerous small ethnolinguistic groups, as reliable self- sufficiency is more easily achieved. The relationship between linguistic diversity and the modem economy is also investigated. Some support is found for the Fishman-Fool hypothesis which states that linguistic diversity is negatively related to economic well-being. The third section deals with diversity in linguistic structure, concentrating on the sound system. It is argued that the size of the phonological inventory and the vowel/consonant ratio are the result of trade-offs between competing articulatory and perceptual motivations. This hypothesis is supported by an analysis of word-1 ength in twelve West African languages. It is further hypothesised that different societal contexts might favour different balances between the two motivations, with languages used over a wide area tending towards simple inventories and long words. This prediction is borne out for West Africa, though it does not seem to hold at a global level. ACKNOWLEDGEMENTS My three years of research were funded by the Medical Research Council, which continues to support Anthropology even though it falls outside its main and more vital remit. I have been extremely lucky to be based in the department of Anthropology at UCL, which is an eclectic and often inspiring place. I am grateful above all to my supervisors, Robin Dunbar and Leslie Aiello, for getting me started on this track, for having the patience to let me find out where it was heading, and then for keeping me going towards the end. Thanks are also due to Fred Brett, Ruth Mace, Mark Pagel, Sara Randall, and Simon Strickland for help along the way. A number of academics from outside my department have also encouraged me greatly by devoting time and interest to my work; they include Mai ami Buba, Ron Cosper, Dick Hudson, Simon Kirby, Chris Knight, Bjom Lindblom, Camilla Power and Maggie Tallerman. As writing up loomed, Richard Bruce and everyone in Chanso got me inspired about West Africa and the prospect of further research. I hope it is no slight to my supervisors to say that as a graduate student you leam more from your peers than from anywhere else. I owe a special debt to all the other graduate students at UCL, who have been good teachers and good friends, especially Jo Abbott, Louise Barrett, Adam Biran, Dan Brockington, Pippa Chenevix- Trench, Alan Dangour, Emmanuel de Merode, Nilofer Ghaffar, Tania King, Hilda Kiwasila, Victoria Malkin, Sian Sullivan, and Daisy Williamson. TABLE OF CONTENTS Title page 1 Abstract 2 Acknowledgements .......................................................................................................3 Table of contents ............................................................................................................ 4 List of figures ............................................................................................................ 8 List of tables .......................................................................................................... 11 List of maps .......................................................................................................... 12 1. Introduction ........................................................................................................ 13 1.1 Preamble ........................................................................................................13 1.2 The need for an interdisciplinary approach ........................................... 14 1.3 Language and biology ...............................................................................18 1.4 Organisation of the thesis ..........................................................................19 2. The Mechanics of Linguistic Diversity...........................................................20 2.1 Introduction .................................................................................................. 20 2.2 Mechanisms of linguistic diversification ................................................22 2.2.1 Imperfect learn in g ......................................................................... 22 2.2.2 Geographical isolation ..................................................................25 2.2.3 Social selection .............................................................................. 27 2.2.4 Functional selection .......................................................................29 2.2.5 Mechanisms of diversification: summary .................................34 2.3 Computer simulations .................................................................................35 2.3.1 The use of sim ulations ..................................................................35 2.3.2 Methods ...........................................................................................36 2.3.3 Basic re s u lts ................................................................................... 40 2.3.3.1 The continuous case ...................................................... 40 2.3.3.2 The discrete case ........................................................... 46 2.3.4 More realistic social structures ...................................................49 2.3.4.1 The continuous case ...................................................... 50 2.3.4.2 The discrete case ........................................................... 50 2.3.5 Social selection .............................................................................. 53 2.3.5.1 The continuous case ...................................................... 54 2.3.5.2 The discrete case ........................................................... 54 2.3.6 Functional selection .......................................................................56 2.3.6.1 The continuous case ...................................................... 57 2.3.6.2 The discrete case ........................................................... 58 2.4 D iscussion .....................................................................................................62 3. Diversity in Space: A West African Case Study .......................................68 3.1 Introduction .................................................................................................. 68 3.1.1 Quantifying linguistic diversity ...................................................70 3.2 Linguistic diversity in West Africa .......................................................... 72 3.3 Geographical influences on the distribution of languages ..................76 3.3.1 Physical isolation ......................................................................... 76 3.3.2 Political organisation .................................................................... 80 3.3.3 T ra d e ................................................................................................82 3.3.4 T ran sp o rt .........................................................................................82 3.3.5 The extent of generalised exchange ........................................... 83 3.4 Ecological risk and social network .......................................................... 85 3.5 Testing the theory ......................................................................................89 3.5.1 Data collection .............................................................................. 89 3.5.1.1 Measures of linguistic diversity ....................................89 3.5.1.2 Ecological and relief measures ...................................... 89 3.5.2 R esu lts............................................................................................. 90 3.5.2.1 Choosing among the ecological measures ..................90 3.5.2.2 Testing hypotheses 1, 2 and 3 ......................................96