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About this book
About this book
Why do baby sharks, hyenas, and pelicans kill their siblings? Why do beetles and mice commit infanticide? Why are twins and birth defects more common in older human mothers? A Natural History of Families concisely examines what behavioral ecologists have discovered about family dynamics and what these insights might tell us about human biology and behavior. Scott Forbes's account describes an uneasy union among family members in which rivalry for resources often has dramatic and even fatal consequences.
In nature, parents invest resources and control the allocation of resources among their offspring to perpetuate their genetic lineage. Those families sometimes function as cooperative units, the nepotistic and loving havens we choose to identify with. In the natural world, however, dysfunctional familial behavior is disarmingly commonplace.
While explaining why infanticide, fratricide, and other seemingly antisocial behaviors are necessary, Forbes also uncovers several surprising applications to humans. Here the conflict begins in the moments following conception as embryos struggle to wrest control of pregnancy from the mother, and to wring more nourishment from her than she can spare, thus triggering morning sickness, diabetes, and high blood pressure. Mothers, in return, often spontaneously abort embryos with severe genetic defects, allowing for prenatal quality control of offspring.
Using a broad sweep of entertaining examples culled from the world of animals and humans, A Natural History of Families is a lively introduction to the behavioral ecology of the family.
Preface xi Chapter 1: Blame Parents 1 Do the Good Die Young? 3 The Family Myth 5 Chapter 2: The Optimistic Parent 9 The Evolution of Family Size 9 The Puzzle of Obligate Brood Reduction 10 How Many Babies? 11 Avian Families 16 Core and Marginal Offspring 16 Asymmetric Sibling Rivalr Creates Disposable Offspring 18 The Evolution of Family Structure 19 What Is Parental Optimism? 21 Why Parental Optimism? 23 Tracking Erratic Resources 23 Replacement 27 Facilitation 28 Multiple Incentives for Parental Optimism 29 Are Humans Optimistic Parents? 31 Chapter 3: Why Parents Play Favorites 32 Mom Always Liked You Best 32 The Fivefold Advantage of Favoritism 33 1. The Benefits and Costs of Unequal Parental Investment 34 2. Divestment of Unneeded Offspring 36 3. Benefits of Diversification 39 4. Correcting Earlier Decisions 41 5. Bet Hedging and Brood Reduction 41 Chapter 4: How Parents Play Favorites 43 What Is a Phenotypic Handicap? 43 How Birds Play Favorites 44 Primar Versus Secondar Handicaps 44 How Blackbirds Play Favorites 45 Reversible Handicaps 46 How Marsupials Play Favorites 47 Brood Reduction in Rabbits 49 How Plants Play Favorites 50 Different Species, Same Idea 51 Humans Play Favorites Too 52 Birth Order and Favoritism 53 Chapter 5: Family Conflict 55 Genetic Conflict between Parents and Offspring 55 Parent-Offspring Conflict 57 Pregnancy and Parent-Offspring Conflict 58 Natural-Born Cancers 60 Imprinted Genes in Humans 62 Genetic Conflict and Beckwith-Wiedemann Syndrome 64 Parent-Offspring Conflict over Embryo Growth 64 Imprinting and Gestational Diabetes 65 Pregnancy Sickness and Genetic Conflict 66 HCG: The Hormone of Pregnancy Sickness? 68 Evolution of Chorionic Gonadotropins in Primates 70 Chorionic Gonadotropins and Miscarriage 70 Chapter 6: Selfishness Unconstrained 78 Brood Parasitic Birds 79 Old World Cuckoos 79 ... and New World Cowbirds 80 Cowbird Mafia? 80 Cuckoo Catfish 81 The Origins of Brood Parasitism 81 Adopting Runaways? 82 Forced Adoption of Nonkin 83 Voluntar Adoption of Nonkin 85 The Lesson of Brood Parasitism 86 Chapter 7: Screening for Offspring Quality 87 The Logic of Progeny Choice 87 Sequential versus Simultaneous Progeny Choice 88 Progeny Choice in Humans 89 Adaptive Miscarriage 90 Chromosomal Defects in Humans 91 Sex Chromosomes and Birth Defects 94 Turner's Syndrome and Genomic Imprinting 96 Birth Defects and Maternal Age 96 Rejecting Low-Quality Embryos 97 HCG and Adaptive Miscarriage 98 Relaxed Screening in Older Mothers? 100 Why Relaxed Selection? 103 Why More Spontaneous Abortions in Older Mothers? 104 The Origin of Genetic Defects 105 The Shadow of Menopause 105 Screening, Maternal Age, and the Role of Genomic Imprinting 106 Maternal Age and Twinning 108 Chapter 8: Why Twins? 109 The Evolution of Brood and Family Size 109 Fault-Tolerant Design in Humans 111 Twinning as an Insurance Strategy 112 Insurance Offspring in Birds 113 In Vitro Fertilization and Twinning 114 Age, Trisomy 21,and Twinning 117 More Than Just Polyovulation 118 Twinning and Individual Optimization 121 Fit or Fat? 124 A Womb for Two 126 Natural Selection on Twinning Frequency 126 Brood Reduction before Birth? 127 Chapter 9: Fatal Sibling Rivalry 129 Siblicide 129 Desperado Siblings Result from Extreme Favoritism 132 The Good and the Best 133 Facultative Versus Obligate Brood Reduction 135 Ultraselfish Alleles 137 Human Twins 139 "Biological" Influences 144 Chapter 10: Family Harmony 147 Cooperation in Families 147 The Arthur Dent Effect 148 Why Cooperation? 148 The Road to Cooperation 150 Parental Optimism and the Evolution of Cooperation 151 Polyembryony and New Roles for Marginal Offspring 152 Parasitoid Wasps 153 Adaptive Suicide? 154 The Benefits of Teamwork 156 Social Insects: The Ultimate Team Players 157 Trophic Offspring 160 Sibling Synergies in Birds and Mammals 160 Conflict When Necessary, but Not Necessarily Conflict 162 Cooperative Defense ... against Parents? 166 Facilitation in Humans? 167 Finding Their Niche: Birth Order and Human Behavior 168 Chapter 11: Cannibalism and Infanticide 171 The Pathways to Cannibalism 171 Honey, I Ate the Kids 171 Offspring Designed to be Eaten 174 The Pathways to Infanticide 175 Sexually Selected Infanticide 175 Killer Rodents 176 Infanticide in Families 178 The Unwilling Parent? 178 Chapter 12: Brave New Worlds 182 Artificial Parental Optimism and Infanticide 184 An Epidemic of Multiple Births 185 Risks of Multiple Gestation 186 The Ghost in the Machine 187 Embryo Reduction 188 Artificial Progeny Choice 189 Refining Artificial Progeny Choice 190 Does Assisted Reproduction Cause Low-Quality Progeny? 191 Send in the Clones 192 Parental Optimism and the Law of Unintended Consequences 194 Blame Parents 195 Chapter 13: Debunking the Family Myth 197 Selected References 201 Index 229
Scott Forbes, Professor of Biology at the University of Winnipeg, is a behavioral ecologist whose chief research interest is the evolutionary ecology of families. He has published articles in a wide variety of journals, including "Behavioral Ecology and Sociobiology, Ecology, Nature, American Naturalist", and "Trends in Ecology & Evolution".