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Princeton University Press
A Natural History of Families

A Natural History of Families

by Scott ForbesScott Forbes


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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 engaging 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.

Product Details

ISBN-13: 9780691130354
Publisher: Princeton University Press
Publication date: 01/22/2007
Edition description: New
Pages: 256
Product dimensions: 6.00(w) x 9.25(h) x (d)

About the Author

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.

Table of Contents

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

What People are Saying About This


An outstanding contribution to the literature on the evolution of human social behavior, this book breaks new ground and, most importantly, frames the family exactly where it should be—in an evolved pattern of behavior in which parents seek to enhance their reproductive success, sometimes at the expense of some of their children.
Craig B. Stanford, University of Southern California, author of "Upright: The Evolutionary Key to Becoming Human"

Robin Dunbar

This book is excellent. Having started reading it, I could not put it down but read it all at one go in a day. Extremely readable, it deals elegantly and succinctly with some of the more complex issues and topics in behavioral ecology of parental investment strategies. It will appeal not only to general readers with an interest in animal and human behavior but to students and academics as well.
Robin Dunbar, University of Liverpool, author of "Grooming, Gossip, and the Evolution of Language"

From the Publisher

"This book is excellent. Having started reading it, I could not put it down but read it all at one go in a day. Extremely readable, it deals elegantly and succinctly with some of the more complex issues and topics in behavioral ecology of parental investment strategies. It will appeal not only to general readers with an interest in animal and human behavior but to students and academics as well."—Robin Dunbar, University of Liverpool, author of Grooming, Gossip, and the Evolution of Language

Customer Reviews