I Introductory Comments from a Biological Scientist.- II Introductory Comments from a Social Scientist.- I Genetic Influences on Fertility Motivation and Fertility Outcomes.- 1 Evolutionary Causes of GeneticVariation In Fertility and Other Fitness Components.- 2 Genetic Influences on Childbearing Motivation: Further Testing a Theoretical Framework.- 3 Genetic Influences on Fertility Behavior: Findings From a Danish Twin Study, 1910-1923.- 4 Genetic and Environmental Influences on Fertility Expectations and Outcomes using NLSY Kinship Data.- 5 A Heritability Study of Childbearing MotivationTargetID.- Commentary Commentary on Chapters 1-5.- II Genetic Influences on Pubertal Development and Reproductive Strategies.- 6 Conditional and Alternative Reproductive Strategies: Individual Differences in Susceptibility to Rearing Experience.- 7 Environmental and Genetic Influences on Pubertal Development: Evolutionary Life History Traits?.- 8 Behavior Genetic Modeling of Menarche in U.S. Females.- 9 Early Family Environment, Reproductive Strategy, and Contraceptive Behavior: Testing a Genetic Hypothesis.- Commentary Commentary on Chapters 6-9.- III Genetic Influences on Sexuality, Marriage. and Reproduction.- 10 The Genetics of Human Sexual Orientation.- 11 Endophenotypes for Marital Status in the NAS-NRC Twin Registry.- 12 Age at First Childbirth: A Major Selective Factor for Psychiatric Genes in the Twentieth Century.- 13 Twinning, Fertility, and the Opportunity for Natural Selection in a Micronesian Island Population.- 14 Associations between the Endothelial Nitric Oxide Synthase Gene (NOS3), Reproductive Behaviors, and Twinning.- Commentary Commentary on Chapters 10-14.