Are We Slaves to our Genes? PDF
Preview Are We Slaves to our Genes?
ARE WE SLAVES TO OUR GENES? There is a common misconception that our genomes all unique, except for thoseinidenticaltwins havetheupperhandincontrollingour destiny.The latestgeneticdiscoveries,however,donotsupportthatview.Althoughgenetic variationdoesinfluencedifferencesinvarioushumanbehaviourstoagreateror lesser degree, most of the time this does not undermine our genuine free will. Genetic determinism comes into play only in various medical conditions, notably some psychiatric syndromes. Denis R. Alexander here demonstrates that we are not slaves to our genes. He shows how a predisposition to behave incertain waysisinfluencedat amolecularlevelby particulargenes.Yetafar greaterinfluenceonourbehavioursareourworldviewsthatliebeyondscience andthathaveanimpactonhowwethinkthelatestgeneticdiscoveriesshould,or should not, be applied. Written in an engaging style, Alexander’s book offers toolsforunderstandingandassessingthelatestgeneticdiscoveriescritically. denis r. alexander is the Founding Director (Emeritus) of The Faraday InstituteforScienceandReligionandEmeritusFellowofStEdmund’sCollege, Cambridge.TheformerchairoftheMolecularImmunologyProgrammeatThe Babraham Institute in Cambridge, he helped to establish the National Unit of HumanGeneticsattheAmericanUniversityHospitalinBeirut,Lebanon. Heis theauthorofGenes,Determinism,andGod. Published online by Cambridge University Press Published online by Cambridge University Press Are We Slaves to Our Genes? denis r. alexander UniversityofCambridge Published online by Cambridge University Press UniversityPrintingHouse,Cambridgecb28bs,UnitedKingdom OneLibertyPlaza,20thFloor,NewYork,ny 10006,USA 477WilliamstownRoad,PortMelbourne,vic 3207,Australia 314 321,3rdFloor,Plot3,SplendorForum,JasolaDistrictCentre, NewDelhi 110025,India 79AnsonRoad,#06 04/06,Singapore079906 CambridgeUniversityPressispartoftheUniversityofCambridge. ItfurtherstheUniversity’smissionbydisseminatingknowledgeinthepursuitof education,learning,andresearchatthehighestinternationallevelsofexcellence. www.cambridge.org Informationonthistitle:www.cambridge.org/9781108426336 doi:10.1017/9781108566520 ©DenisR.Alexander2020 Thispublicationisincopyright.Subjecttostatutoryexception andtotheprovisionsofrelevantcollectivelicensingagreements, noreproductionofanypartmaytakeplacewithoutthewritten permissionofCambridgeUniversityPress. Firstpublished2020 AcataloguerecordforthispublicationisavailablefromtheBritishLibrary. LibraryofCongressCataloginginPublicationData names:Alexander,Denis,author. title:Areweslavestoourgenes?/DenisR.Alexander. description:Cambridge,UnitedKingdom;NewYork,NY:Cambridge UniversityPress,2021.|Includesbibliographicalreferencesandindex. identifiers: lccn 2020019423(print)|lccn 2020019424(ebook)| isbn 9781108426336(hardback)|isbn 9781108445054(paperback)| isbn 9781108566520(epub) subjects: mesh:Genetics,Behavioral|GeneticPhenomena|Genetic PredispositiontoDisease classification: lcc qh442 (print)|lcc qh442 (ebook)|nlm qu 450|ddc 572.8 dc23 LCrecordavailableathttps://lccn.loc.gov/2020019423 LCebookrecordavailableathttps://lccn.loc.gov/2020019424 isbn 978 1 108 42633 6Hardback isbn 978 1 10844505 4Paperback CambridgeUniversityPresshasnoresponsibilityforthepersistenceoraccuracyof URLsforexternalorthird partyinternetwebsitesreferredtointhispublication anddoesnotguaranteethatanycontentonsuchwebsitesis,orwillremain, accurateorappropriate. Published online by Cambridge University Press Contents ListofFigures pagevi Preface vii 1. GeneticConfusion 1 2. GeneticInformationandHowItFlows 17 3. GenesandEnvironmentsinHumanDevelopment 36 4. WhatIsBehaviouralGenetics? 55 5. GenesandMentalHealth 74 6. Genes,EducationandIntelligence 94 7. Genes,PersonalityandPersonalityDisorders 111 8. Genes,Food,ExerciseandWeight 130 9. Genes,ReligiosityandPoliticalCommitment 143 10. GayGenes?GeneticsandSexualOrientation 155 11. AreWeSlavestoOurGenes? 178 12. GenesandHumanIdentity 196 Notes 215 DefinitionsofTechnicalTerms 221 References 225 Index 239 v Published online by Cambridge University Press Figures 1.1. PedigreeofaLebanesefamilyshowingtheinheritanceoffructose 1,6-diphosphatasedeficiency.FromAlexanderetal.(1985). page3 2.1. TheDNAdoublehelix.Reproducedbypermissionofthe TempletonPress. 20 2.2. Thegeneticcode.ReproducedfromOpenStax,Biology, OpenStaxCNX. 22 2.3. ReadingDNA. 25 2.4. HowtomakemessengerRNA(mRNA). 25 2.5. Transcriptionandtranslation.Reproducedbypermissionofthe TempletonPress. 26 5.1. TheroleoftheUBEgeneinautismandAngelmansyndrome. BasedondatafromYietal.(2015). 80 7.1. Geneticcorrelationsbetween23andMeindividualsandpsychiatric disorders.FromLoetal.(2017). 116 7.2. ADutchfamilyinwhichamutationinthemonoamineoxidaseA genecausesacompletelackofthemonoamineoxidaseprotein. FromBrunneretal.(1993a). 126 9.1. Acomparisonbetweenidenticalandnon-identicaltwinsinterms of(9.1a)theirfrequencyofcontactand(9.1b)theiremotional closeness.AdaptedfromFigure1ofNeyer(2002). 147 10.1. Thedevelopmentofsame-sexattraction(SSA)inaUS demographicsample.Adapted,withpermission,fromPew ResearchCenter(2013)AsurveyofLGBTAmericans:Attitudes, ExperiencesandValuesinChangingTimes.Washington,DC: PewResearchCenter. 158 vi Published online by Cambridge University Press Preface The aim of this book is to investigate whether the field of behavioural geneticsprovidesanythreatsorchallengestooursenseofhumanfreedom. Arewereallyslavestoourgenes? The book started life as the Gifford Lectures given at St Andrews University in 2012, published under the title Genes, Determinism and God (Cambridge University Press) in 2017. Out of that came the request to publishapopularversionofsimilarmaterialmoreaccessibletothegeneral readerwithout,necessarily,anybackgroundingenetics.Thisisthatversion. Those who have already read Genes, Determinism and God will recognise somesimilarities.However,thisbookcontainsseveralaltogethernewchap- ters, such as Chapter 1, which provides a basic introduction to DNA and genetics,Chapter5,whichdescribesthelatestfindingsinthefieldofgenetics andmentalhealth,andChapter8,whichlooksattheroleofgeneticvariation in differences in our physical size and shape. The science has also been updated as hundreds more papers and books continue to be published in thisrapidlymovingfield.Referencesaregiventotherelevantliteraturefor thosewhowishtofollowupfurther.Theuseofsometechnicallanguageis inevitable when explaining some of the concepts involved, but technical terms are explained when first mentioned and are defined in a separate handylist. Abookonpopulargeneticstouchesdeeplyonourownhumanidentity,so the book covers the influence, or claimed influence, of human genetic variation on differences in our mental health, intelligence, educational attainment,personality,size,weight,levelsofreligiousandpoliticalcommit- ments,sexualorientationandmuchelsebesides,sohopefullythereissome- thing here for everybody. And after surveying these various aspects of our well-being–orotherwise–wethentacklethephilosophicalquestionasto whether our deep sense of free will is at all threatened by genetic vii https://doi.org/10.1017/9781108566520.001 Published online by Cambridge University Press viii PREFACE determinism, finally outlining some competing world views that make a huge difference to our concept of human identity in light of the latest findingsinbehaviouralgenetics. My thanks are due to the many friends and colleagues who have made helpfulsuggestionsonearlierversionsofthepresenttext;inparticular,my thanks go to Keith Fox, Julian Rivers and Leland Taylor. As always, the author is fully responsible for any errors that remain. I would also like to thankChrisAkhurstforhissubeditingandBeatriceRehl,CarolineMorley and Gayathri Tamilselvan at Cambridge University Press for their helpful supportandadvice. https://doi.org/10.1017/9781108566520.001 Published online by Cambridge University Press 1 Genetic Confusion T hepatientwasatinybaby,just2daysold,breathingabnor- mallyfast.Eventuallythingssettleddownandthebabywassenthome. Butinthemonthsthatfollowed,herparentskeptbringingherbacktoA&E withseverebreathingdifficultiesandbloodthatwasabnormallyacidic.Each time,atinysampleofbloodwastakenfortests.Whatmightbegoingon? Theyearwas1984andthiswastheNationalUnitofHumanGeneticsat theAmericanUniversityHospitalinBeirut,Lebanon.Ihadgonethereafew yearsearliertosetupanewlaboratoryofbiochemicalgeneticsaspartofthe Unit. This was a country where consanguineous1 marriages between first cousinswerecommon.Butthislittlebabycamefromnon-relativesandthere was no clue from the family history as to what might be happening.There canbeamyriadofreasonsforabnormallyacidicblood(‘lacticacidosis’).The firsttwotimesthebabywasbroughttoA&E,theenzymeswetestedturned outtobenormal. Thiswasfollowedbymorehoursinthelibrarysearchingtheliterature(no onlinedigitalresourcesinthosedays!).Coulditpossiblyinvolveaveryrare deficiency of fructose 1,6-diphosphatase? This is an enzyme required for breaking down fructose – a sugar found especially in honey and mature fruit – essential for making cellular energy from the fructose. Without it, fructoseisconvertedtolacticacid,soacidifyingtheblood.Wesetupthetest using leucocytes (white blood cells) from control blood, ready for the next opportunity. Sure enough, the baby was soon back in A&E again and this time we nailed it: the fructose 1,6-diphosphatase levels in the baby’s blood werebarelydetectable–problemsolved,onlythethirty-ninthreportedcase intheworld(Alexanderetal.,1985).Itturnedoutthat,duetoherfailureto thrive, anxious relatives had been dosing the little girl with honey – 1 https://doi.org/10.1017/9781108566520.002 Published online by Cambridge University Press 2 1 GENETICCONFUSION unwittinglynearlykillingherintheprocess.Allthatneededtohappenwas forthegirltobeplacedonalow-fructosedietandallwouldbewell. Ihavesometimeswonderedwhathappenedtothatlittlegirl,whomustnow beawomaninhermid-30s.Didshegetmarriedandhaveafamily?Hasshe kept toher diet and so maintained her goodhealth? Ofcourse,hersamples were(quiteproperly)allanonymouswhentheyarrivedinthelaboratory,so I willneverknow. She was from a SunniMuslimfamily. Lessfortunatewas a baby boy aged 18 months who presented at the hospital around the same time with convulsions followed by irreversible coma and death on his sixth day in hospital. He was the first child of consanguineous parents from the LebaneseDruzecommunity.Hisfructose1,6-diphosphatasewasalsodeficient (Alexander et al., 1985). Two of his first cousins, also the product of aconsanguineousmarriage,hadpreviouslydiedattheageof2years.Hadit beenpossibletodetecttheirdeficiencywithinthefirstfewmonthsoflife,they wouldallbealivetoday. Outside the hospital walls, the Lebanese civil war continued to rage and hundredsweredying.Butgeneticallytherewerewinnersandlosersaswell. And in some cases, at least, if only the consequences of the genetic defect could be identified early enough – in this case an absent enzyme – then it meantliferatherthandeath. 1.1 Mendel’sInheritance TounderstandhowtheenzymedeficiencydetectedinthoseLebanesebabies is passed on through families, we need to go back to an Augustinian Moravian monk named Gregor Mendel (1822–1884). In the sheltered space of St Thomas’s Abbey in Brno (now in the Czech Republic) where he was friarandabbot,Mendelcarriedoutapainstakingseriesofbreedingexperi- ments in which he bred nearly 30,000 pea plants of carefully selected varieties. Mendel’s experiments revealed several key findings. The varieties of pea plantsthathestartedwithbredtrueformanygenerations.Today,wewould say that they were genetically pure lines. Thiswasan important factor in his success. When Mendel cross-hybridised these different varieties, the traits inherited by the next generation of peas (the ‘hybrids’) were ‘particulate’ – their seeds were either wrinkled or smooth, or the plants were either tall or short.Thehybridsshowedonlyoneofthetwopossiblecharactertraitspresent in the parents, inconsistent with the idea of ‘blending inheritance’ in which different traits merged with each other. Mendel also noticed that some traits were ‘dominant’ and some were ‘recessive’. When he crossed the tall pea https://doi.org/10.1017/9781108566520.002 Published online by Cambridge University Press
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