In 1951, the geneticist Luigi Luca Cavalli-Sforza was teaching in Parma when a student--a priest named Antonio Moroni--told him about rich church records of demography and marriages between relatives. After convincing the Church to open its records, Cavalli-Sforza, Moroni, and Gianna Zei embarked on a landmark study that would last fifty years and cover all of Italy. This book assembles and analyzes the team's research for the first time.
Using blood testing as well as church records, the team investigated the frequency of consanguineous marriages and its use for estimating inbreeding and studying the relations between inbreeding and drift. They tested the importance of random genetic drift by studying population structure through demography of the last three centuries, using it to predict the spatial variation of frequencies of genetic markers. The authors find that drift-related genetic variation, including its stabilization by migration, is best predicted by computer simulation. They also analyze the usefulness and limits of the concept of deme for defining Mendelian populations. The genetic effect of consanguineous marriage on recessive genetic diseases and for the detection of dominance in metric characters are also studied.
Ultimately bringing together the many strands of their massive project, Cavalli-Sforza, Moroni, and Zei are able to map genetic drift in all of Italy's approximately 8,000 communes and to demonstrate the relationship between each locality's drift and various ecological and demographic factors. In terms of both methods and findings, their accomplishment is tremendously important for understanding human social structure and the genetic effects of drift and inbreeding.
Inhaltsverzeichnis
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
