Consanguinity, Inbreeding, and Genetic Drift in Italy

"[An] extraordinary book, packed with detailed information... A careful reading of this remarkable book will yield much more information."--Walter Bodmer, Nature

Luigi Luca Cavalli-Sforza is Professor of Genetics Emeritus at Stanford Medical School, and Member of the U.S. National Academy of Sciences. His books include "History and Geography of Human Genes" and "Genes, Peoples, and Languages". Antonio Moroni is Professor Emeritus of Ecology at the University of Parma (Italy) and member of the National Academy of Sciences (Academy of XL). Gianna Zei was Professor of Statistics and Biometry at the University of Pavia and directs the population genetics group of the CNR Institute of Molecular Genetics in Pavia.

Acknowledgments ix 1. History of This Investigation and Structure of This Book 1 1.1 Introduction 1 1.2 History of This Research 4 1.3 Consanguinity 9 1.4 Inbreeding Measurement 11 1.5 Inbreeding Effects 13 1.6 Random Genetic Drift 18 1.7 Research on Drift in the Parma Valley 20 1.8 Genetic Uses of Surnames 21 1.9 A Summary of Published Studies on Consanguinity and Inbreeding, with Special Reference to Italy 24 1.10 Structure of This Book 26 2. Customs and Legislation Affecting Consanguineous Marriages, with Special Attention to the Catholic Church 29 2.1 Early and Medieval Christian Tradition 29 2.2 Traditional Methods of Consanguinity Evaluation: The Roman and the German Methods 34 2.3 Justifications of the Dispensation Request 35 3. Demographic Factors Affecting the Frequencies of Consanguineous Marriage-A Study in Northern Emilia 39 3.1 Nature and Interest of the Problem 39 3.2 Relations to Population Structure 40 3.3 Number of Sibs, Distribution of Family Sizes, and Observed Abundance of Relatives 43 3.4 Consanguinity Degrees and Observed Numbers of Consanguinity Dispensations in Northern Emilia 47 3.5 Pedigree Types, Pedigree Codes, and Proofs of the Influence of Age at Marriage and of the Sex of Intermediate Ancestors 52 4. Probability of Consanguineous Marriages 69 4.1 Theory of Age Effects on the Frequency of Consanguineous Marriages 69 4.2 Migration as a Factor Affecting the Frequency of Consanguineous Marriages 76 4.3 The Role of Women in Maintaining Family Ties among Relatives 78 4.4 Observed and Expected Frequencies of Major Consanguinity Degrees 83 5. Consanguinity, Inbreeding, and Observed Genetic Drift in the Parma Valley 90 5.1 The Parma Valley and the Origin of This Investigation 90 5.2 Geography of the Parma Valley 91 5.3 Consanguinity and Inbreeding in the Parma Valley 95 5.4 Blood Groups and Genetic Drift 101 5.5 Surnames and Genetic Drift 115 5.6 Correlations of Inbreeding and Drift 118 6. A Computer Simulation of the Upper Parma Valley Population 122 6.1 The Need for a Population Simulation 122 6.2 Structure of the Simulation 123 6.3 The Migration Matrix 129 6.4 Is Drift the Only Cause of Genetic Variation in the Parma Valley? 134 6.5 Expected and Observed Consanguinity 142 7. Islands 149 7.1 Italian Islands 149 7.2 Sardinia 149 7.3 Sicily 175 7.4 Aeolian Islands 183 8. Effects of Inbreeding on Normal and Pathological Phenotypes 192 8.1 Introduction 192 8.2 Normal Quantitative Phenotypes: Stature and Chest Girth 193 8.3 Mortality, Fertility, and Sterility 196 8.4 Incidence of Disease Groups from Surveys of Hospital Populations 199 8.5 Study of Specific Recessive Diseases 204 9. Consanguineous Marriages in Italy: Data from the Vatican Archives 211 9.1 Introduction 211 9.2 Variations of Consanguinity over Time 212 9.3 Geographical Variations: Provinces and Regions 214 9.4 Space-Time Analysis: Four Models of Declining Consanguinity in Italian Regions 215 9.5 Factors Responsible for Space and Time Differences in Consanguinity: Choice of Variables and Their Meaning 222 9.6 Demographic Variables: Birthrate, Death Rate, and Demographic Transition 223 9.7 Effect on Consanguinity of Environmental Variables of Socioeconomic and Ecological Meaning 229 9.8 An Attempt at a General Synthesis 237 10. Geography of Demes in Italy 242 10.1 Population Sampling 242 10.2 Random Mating, Mendelian Populations, and Demes 246 10.3 Comparing Genetic and Demographic Approaches to the Study of Demes 252 10.4 Are comuni (Communes) Demes? 260 10.5 The Negative Correlation Between N and m 263 10.6 Using Surnames for Evaluating Drift 267 10.7 A Drift Map of Italy by Communes 274 10.8 Statistical Observations on the Italian Drift Map 280 11. Conclusions 284 11.1 Human Consanguinity 284 11.2 Inbreeding 291 11.3 Genetic Drift 293 11.4 Demes, Isolates, and Migration 298 Bibliography 303 Index 313