1. Introduction; 1.1 Preamble; 1.2 The Family Tree Model; 1.3 The Linguistic Item and Linguistic Pool; 1.4 Levels and Diversity in the Linguistic Pool; 1.5 Justification, Disguised as Apology; 1.6 The Need for an Interdisciplinary Approach; 2. Language Evolution: Basic Mechanisms; 2.1 Introduction; 2.2 The Neutral Model; 2.3 Problems with the Neutral Model; 2.4 Additional Amplifiers; 2.5 Summary and Conclusions; 3. Language Evolution: Computer Simulations; 3.1 Introduction; 3.2 The Use of Computer Simulations; 3.3 Methods; 3.4 Basic Results; 3.5 More Realistic Social Structures; 3.6 Social Selection; 3.7 Functional Selection; 3.8 Discrete Traits; 3.9 Discussion; 3.10 Adaptive Significance of Social Selection; 4. Language Diversity: Patterns in Space; 4.1 Introduction; 4.2 Quantifying Language Diversity; 4.3 Vectors of Language Spread; 4.4 Case Studies; 4.5 Ecological Risk as a Universal Constraint; 4.6 Testing the Theory: Methods; 4.7 Testing the Theory: Results; 4.8 Hunter-gatherers; 4.9 Conclusions; 5. Language Diversity: Changes in Time; 5.1 Introduction; 5.2 The Palaeolithic Equilibrium; 5.3 The Neolithic Punctuation; 5.4 The Neolithic Aftershock; 5.5 The Industrial Punctuation; 5.6 Prospect; 6. Phylogenetic Diversity; 6.1 Introduction; 6.2 Lineages and Stocks; 6.3 The Distribution of Stocks; 6.4 Stocks and Time: Nichol's Model; 6.5 Stocks and Time: An Alternative Model; 6.6 Validating the Model; 6.7 Conclusions; 7. Structural Diversity; 7.1 Introduction; 7.2 Causes of Structural Diversity; 7.3 Geographical Distribution of Structural Diversity; 7.4 Case Study: Phonological Inventory and the Lexicon; 7.5 Conclusions; Epilogue; Appendix - Global Language Diversity Data