Genetics and human behaviour : the ethical context

Table of Contents Council membership and terms of reference.................................................................... iii Preface .................................................................................................................................. v Acknowledgements............................................................................................................. vi Working Party membership.............................................................................................. xiii Working Party terms of reference..................................................................................... xv Summary and recommendations...................................................................................... xix Section I: Introduction and context Chapter 1: Introduction........................................................................................................ 3 Why this Working Party is important.................................................................................. 5 Defining the normal range of behavioural characteristics................................................ 7 The scope of research in behavioural genetics .................................................................. 8 The structure of the Report ................................................................................................. 8 Chapter 2: The historical context ...................................................................................... 11 The impact of eugenic thought on research into human behaviour ............................. 18 Psychology in the first half of the twentieth century .......................................... 18 Psychology from the 1960s onwards...................................................................... 20 Individual differences ............................................................................. 20 Evolutionary psychology......................................................................... 21 Processes of development ...................................................................... 21 Conclusion ........................................................................................................................... 22 Section II: Scientific background Chapter 3: Research in behavioural genetics ................................................................... 25 Introduction ........................................................................................................................ 27 What is genetic variation?................................................................................................. 29 What is meant by normal variation in human behaviour? ............................................. 31 ‘A gene for X’? ................................................................................................................... 32 Describing human behaviour ............................................................................................ 35 Predicting human behaviour from genetic information................................................. 35 Conclusion.......................................................................................................................... 36 Chapter 4: Quantitative genetics: measuring heritability .............................................. 37 Introduction ........................................................................................................................ 39 How is population variation examined using genetic studies?....................................... 39 Genetic influences on variation.............................................................................. 39 Genetics and human behaviour: the ethical context viii Environmental influences on variation .................................................................. 41 Gene-environment correlation and interaction .................................................... 41 Family, twin and adoption studies..................................................................................... 42 Family studies ........................................................................................................... 42 Studies of twins........................................................................................................ 42 Methods................................................................................................... 42 Interpretation of twin study findings.................................................... 43 Adoption studies ................................................................................................................. 44 Current uses of quantitative genetic studies .................................................................... 45 Conclusion ........................................................................................................................... 46 Chapter 5: Identifying genetic factors contributing to individual differences in behaviour. 47 Introduction ........................................................................................................................ 49 Approaches to identifying susceptibility alleles ............................................................... 49 Linkage studies ........................................................................................................ 50 Association studies .................................................................................................. 51 Identification of alleles that influence behaviour ................................................ 52 Scaling up the analysis: new methods in genetics ................................................ 52 Conclusion ........................................................................................................................... 53 Chapter 6: Research in behaviour genetics involving animals ...................................... 55 Introduction ........................................................................................................................ 57 How are animal models created?...................................................................................... 58 What are the benefits of using animals to study the genetics of human behaviour?.. 60 What are the problems with using animals to study the genetics of human behaviour? .. 61 Conclusion.......................................................................................................................... 63 Part III: Reviews of the evidence Chapter 7: Intelligence ....................................................................................................... 67 Background........................................................................................................................ 69 Trait definition and measurement .................................................................................... 69 Current findings: quantitative genetics ............................................................................ 71 Current findings: molecular genetics ................................................................................ 73 Directions for future research ........................................................................................... 76 Chapter 8: Personality........................................................................................................ 79 Background......................................................................................................................... 81 Trait definition and measurement .................................................................................... 81 Current findings: quantitative genetics ............................................................................ 83 Current findings: molecular genetics ................................................................................ 84 Quantitative trait loci research............................................................................... 85 Current findings: research involving animals ................................................................... 85 Future directions for research ........................................................................................... 86 ix Chapter 9: Antisocial behaviour........................................................................................ 87 Background........................................................................................................................ 89 Trait definition and measurement .................................................................................... 89 Current findings: quantitative genetics ............................................................................ 91 Antisocial behaviour................................................................................................ 91 Violence.................................................................................................................... 93 Sex differences......................................................................................................... 94 Current findings: molecular genetics ................................................................................ 95 Current findings: research involving animals ................................................................... 95 Future directions from research ........................................................................................ 96 Chapter 10: Sexual orientation ......................................................................................... 97 Background........................................................................................................................ 99 Trait measurement and definition .................................................................................... 99 Current findings: quantitative genetics .......................................................................... 100 Families ............................................................................................................... 100 Twins and adopted siblings .................................................................................. 101 Male homosexuality ............................................................................. 101 Female homosexuality.......................................................................... 102 Current findings: molecular genetics .............................................................................. 102 Current findings: research involving animals ................................................................. 103 Current findings: other biological influences................................................................. 104 Critical assessment of the validity of this evidence.........................................................105 Evolutionary arguments against genetic influences on homosexuality ....................... 106 Future directions for research ......................................................................................... 107 Chapter 11: Themes from the reviews of the evidence................................................ 109 Introduction ...................................................................................................................... 111 The difficulty of defining and measuring traits ............................................................. 111 Estimates of heritability ................................................................................................... 111 The lack of replicated findings in molecular genetics ................................................... 112 Applications of current research findings....................................................................... 112 Reporting research in behavioural genetics ................................................................... 113 Funding research in behavioural genetics ...................................................................... 114 Conclusion ......................................................................................................................... 115 Part IV: Ethical, legal, social and policy issues Chapter 12: Genetics, freedom and human dignity ...................................................... 119 The material self ............................................................................................................... 122 Determinism and fatalism................................................................................................ 123 Freedom, possibility and rationality................................................................................ 124 Eliminating rationality .......................................................................................... 125 Accommodating rationality.................................................................................. 126 x The implications of behavioural genetics ....................................................................... 128 Conclusion ......................................................................................................................... 130 Chapter 13: Selecting and changing behavioural traits............................................... 131 Introduction ...................................................................................................................... 133 Will there be any practical applications of research in behavioural genetics ............. 133 Genetic interventions ............................................................................................ 134 Medical interventions............................................................................................ 135 Environmental interventions ................................................................................ 135 ‘Medicalising’ human behaviour ..................................................................................... 135 Stigma............................................................................................................................... 139 Evaluating different ways of changing ourselves .......................................................... 140 Effectiveness........................................................................................................... 140 Safety ..................................................................................................................... 140 Reversibility............................................................................................................ 142 Choice .................................................................................................................... 142 Intervention and individuality.............................................................................. 143 Therapy versus enhancement .............................................................. 144 Access to interventions..................................................................................................... 145 Monitoring the provision of genetic tests and interventions ....................................... 146 Prenatal selection ............................................................................................................. 148 Technologies for prenatal testing and selection................................................. 148 Selection on non-clinical grounds: ethical arguments ....................................... 150 For selection .......................................................................................................... 152 The right to procreative autonomy..................................................... 152 Against selection ................................................................................................... 153 The ‘expressivist’ argument.................................................................. 153 Equality.................................................................................................. 153 Natural humility.................................................................................... 154 Chapter 14: Legal responsibility..................................................................................... 157 The history of biological explanations of human behaviour in law............................. 159 Previous genetic and physiological explanations of crime............................................ 160 XYY males .............................................................................................................. 160 Syndromes.............................................................................................................. 161 Genetics: Huntington’s disease............................................................................. 161 Genetics: Monoamine oxidase A (MAOA) deficiency ......................................... 161 Genetic information as an exculpatory factor ............................................................... 162 Sentencing and treatment of offenders ......................................................................... 166 Predictive use of genetic information............................................................................. 168 Conclusion ......................................................................................................................... 171 xi Chapter 15: Testing and selection in employment, education and insurance ........... 173 Employment..................................................................................................................... 177 The current legal framework................................................................................ 177 Discrimination laws ............................................................................................... 178 Unfair dismissal...................................................................................................... 180 Privacy and confidentiality ................................................................................... 180 Earlier reform proposals ....................................................................................... 181 Testing for behavioural traits ............................................................................... 182 Education .......................................................................................................................... 183 Insurance .......................................................................................................................... 185 Appendix 1: Methods of working ................................................................................... 191 Appendix 2: Consultation with the public...................................................................... 195 Glossary ............................................................................................................................. 205 Glossary of Abbreviations and Acronyms ....................................................................... 211