/ 襯襯 or ー 4 / びム 47 Other genes for its own selfish ends. SO does a gene for crossmg— over. There are even genes—called mutators—which manipulate the rates 0f copymg-errors in other genes. BY definition, a COPY- mg error IS tO the disadvantage Of the gene which is mscopied. But if it is t0 the advantage 0f the selfish mutator gene which induces it, the mutator can spread through the gene P001. Similarly, if crossmg—over benefits a gene for crossmg-over, that IS a sufficient explanation for the existence Of crossmg—over. And if sexual, as opposed tO non-sexual, reproduction benefits a gene for sexual reproduction, that is a sufficient explanation for the existence Of sexual reproduction. Whether or not it benefits all the rest Of an individual's genes IS comparatively irrelevant. Seen from the selfish gene s point Of view, sex is not SO bizarre after all. ThiS comes perilously close tO being a circular argument, S1nce the existence Of sexuality is a precondition for the whOle chain Of reasoning which leads t0 the gene being regarded as the unit 0f selection. I believe there are ways Of escaping from the circular- ity, but this bOOk is not the place tO pursue the question. Sex exiStS. That much iS true. lt iS a consequence Of sex and crossing— over that the small genet1C unit or gene can be regarded as the nearest thing we have tO a fundamental, independent agent Of evolution. Sex is not the only apparent paradox which becomes less puzz- ling the moment we learn tO think in selfish gene terms. For lnstance, it appears that the amount Of DNA in orgamsms IS more than is strictly necessary for building them: a large fraction 0f the DNA is never translated intO protein. From the point Of view Of the individual organism this seems paradoxical• If the purpose of DNA is to supervise the building 0f bodies, it is surprising t0 find a large quantity 0f DNA which does no such thing. Bi010gists are racking their brains trying t0 think what useful task this apparently surplus DNA is doing. But from the P0int 0f view of the selfish genes themselves, there is no paradox. The true purpose' Of DNA iS tO more and no less. sim¯ plest way t0 explain the surplus DNA is t0 suppose that it is a parasite, or at best a harmless but useless passenger, hitching a ride in the survival machines created by the 0ther DNA. Some people (b)ect tO what they see as an excessively gene- centred view 0f evolution. After all, they argue, it is whole

94 月 gg 〃・・立 4 ん方り 4 〃ノビ覊川“ん substantial Proportion 0f their genes. Each selfish gene therefore has its loyalties divided between different bodies. This is ex- plained in the next chapter.

外 1 ど川い . ・一んど〃どル r ど 2 / 耘 4 ー 0 ハ however, makes them behave rather as if they were purposeful, and it has been convenient, as a shorthand, tO refer tO genes in the language 0f PUrPOSe. For example, when we say genes are trying tO increase their numbers in future gene pools', what we really mean iS 'those genes WhiCh behave ln such a way as tO increase their numbers in future gene POOIS tend tO be the genes whose effects we see in the world'. Just as we have found it convenient to think of genes as active agents, working purposefully for their own survival, perhaps it might be convenient tO think Of memes in the same way. ln neither case must we get mystical about it. ln both cases the idea 0f purpose is only a metaphor, but we have already seen what a fruitful metaphor it is in the case Of genes. We have even used words like 'selfish' and 'ruthless' 0f genes, knowing full well it is only a figure 0f speech. Can in exactly the same spirit, Ok for selfish or ruthless memes? There iS a problem here concerning the nature Of competition. Where there is sexual reproduction, each gene IS competing par- ticularly with its own alleles—rivals for the same chromosomal SlOt. Memes seem tO have nothing equivalent tO chromosomes' and nothing equivalent tO alleles. I suppose there is a trivial sense ln which many ideas can be said tO have opposites'. But in general memes resemble the early replicating molecules' floating chaotically free in the primeval soup, rather than modern genes ln their neatly paired, chromosomal regiments. ln what sense then are memes competing with each Other? Should we expect them tO be 'selfish' or 、 ruthless' if they have no alleles? The answer is that we might, because there is a sense in which they must indulge in a kind Of competition with each Other. Any user Of a digital computer knows hOW precious computer trme and memory storage space are. At many large computer centres they are literally costed in money; or each user may be allOtted a rat10n Of time, measured in seconds, and a ratl()n Of space, measured in 'words'. 、 he computers in which memes live are human brains. Time IS possibly a more lmportant limiting factor than storage space, and it is the subJect Of heavy competi- tion. The human brain, and the body which it controls, cannot d0 more than one or a few things at once. If a meme IS tO dominate the attention Of a human brain, it must dO SO at the expense Of 'rival' memes. other commodities for WhiCh memes are 21 1

んどど〃ど川 ac ん / 〃ど instance in refusing tO have as many children as they are able tO. But in this respect man IS a very special case, as we shall see. What has all this to do with altruism and selfishness? I. am trying tO build up the idea that animal behaviour, altruistic or selfish, is under the control of genes in only an indirect, but still very powerful, sense. By dictating the way survival machines and their nervous systems are built, genes exert ultimate power over behaviour. But the moment—to-moment decisions about what tO dO next are taken by the nervous system. Genes are the primary policy—makers; brains are the exeCUt1Ves. But as brains became more highly developed, they t00k over more and more 0f the actual policy decisions, usmg tricks like learning and simulation in dOing SO. The logical conclusion tO this trend, not yet reached ln any species, would be for the genes tO give the survival mach- lne a single overall policy instruction: dO whatever you think best tO keep us alive. Analogies with computers and with human decision—taking are all very well. But now we must come down tO earth and remem— ber that evolution in fact occurs step-by-step, through the differ- ential survival Of genes in the gene POOI. Therefore, in order for a behaviour pattern—altruistlc or selfish¯to evolve' it IS necessary that a gene 、 for' that behaviour should survwe in the gene POOI more successfully than a rival gene or allele 'for' some different behaviour. A gene for altruistic behaviour means any gene which influences the development Of nervous systems ln such a way as t0 make them likely t0 behave altruistically. ls there any experi- mental evidence for the genet1C inheritance Of altruist1C behaviour? No, but that is hardly surprising, since little work has been done on the genetics 0f any behaviour. lnstead' let me tell you about one study 0f a behaviour pattern which does not hap- pen t0 be obviously altruistic, but which is complex enough t0 be interesting. lt serves as a model for hOW altruistic behaviour might be inherited. Honey bees suffer from an infectious disease called foul brood. This attacks the grubs in their cells. Of the domestic breeds used by beekeepers, some are more at risk from foul brood than others' and it turns out that the difference between strams IS, at least in some cases, a behavioural one. 、 here are SO¯called hygiemc strains which quickly stamp out epidemics by locating infected

5. Aggression: stability and the selfish machine THIS chapter is mostly about the much-misunderstood topic of aggression. Ⅵ第 shall contmue tO treat the individual as a selfish machine, programmed tO dO whatever is best for his genes as a whole. This is the language of convenience. At the end of the chapter we return tO the language Of single genes. TO a survival machine, another survival machine (WhiCh iS not its own child or another close relative) is a part Of its envlron— ment, like a rock or a rlver or a lump Of 応 Od. lt is something that gets in the way, or something that can be exploited. lt differs from a rock or a rlver ln one lmportant respect: lt IS inclined tO hit back. This is because lt t00 IS a machine which holds its lmmortal genes in trust for the future, and it t00 will stop at nothing tO preserve them. Natural selection favours genes which control their survival machines ln such a way that they make the best use Of their envrronment. This includes making the best use Of Other survival machines, bOth Of the same and Of different specles. ln some cases survival machines seem tO impmge rather little on each others' lives. For instance moles and blackbirds dO not eat each Other, mate with each Other, or compete with each Other for living space. Even SO, we must not treat them as completely insulated. They may compete for something, perhaps earth- worms. ThiS does not mean you will ever see a mole and a black— bird engaged in a tug of war over a worm; indeed a blackbird may never set eyes on a mole in its life. But if you wiped out the population 0f moles, the effect on blackbirds might be dramatic, although I could not hazard a guess as to what the details might be, nor by what tortuously indirect routes the influence might travel. Survival machines Of different specles influence each Other in a vanety 0f ways. They may be predators or prey, parasites or hOStS, competitors for some scarce resource. 、 hey may be ex— plOited in special ways, as for instance when bees are used as pollen carriers by flowers.

外イど . ・一んど〃どど 2 ″ ca 知 2 巧 have tO posit genetic advantage ln imltation, though that would certainly help. All that is necessary is that the brain should be 24 みな 0f imitauon: memes will then evolve which exploit the capability to the full. I now close the topic of the new replicators, and end the b00k on a note 0f qualified hope. One unique feature 0f man' which may or may not have evolved memically, is his capacity for con— scious foresight. Selfish genes (and, if you allow the speculation 0f this chapter, memes t00 ) have no foresight. They are uncon— scrous, blind, replicators. The fact that they replicate, together with certain further conditions means, willy nilly, that they will tend towards the evolution ofqualities which, in the special sense Of this book, can be called selfish. A simple replicator, whether gene or meme, cannot be expected tO forgo short—term selfish advantage even ifit would really pay it, in thelong term, t0 d0 so. We saw this in the chapter on aggression. Even though a 、 conspiracy 0f doves would be better for れでり , 朝ん市 0 ″ 4 / than the evolutionarily stable strategy, natural selection is bound t0 favour the ESS. lt is possible that yet another umque quality 0f man is a capacity for genuine, disinterested, true altruism. I hope SO' but I am not gotng tO argue the case one way or the ()ther' nor tO speculate over its possible mem1C evolution. The point I am making now is that, even if we lOOk on the dark side and assume that individual man is fundamentally selfish, our conscious 応 re - sight—our capaclty tO simulate the future ln imagination¯could save us from the worst selfish excesses Of the blind replicators. We have at least the mental equlpment tO foster our long—term selfish interests rather than merely our short-term selfish inter— ests. 嶬 can see the long-term benefits Of participattng in a consplracy Of doves', and we can sit down together tO discuss ways 0f making the conspiracy work. We have the power t0 defy the selfish genes 0f our birth and, if necessary, the selfish memes Of our indoctrination. we can even discuss ways Of deliberately cultivating and nurturing pure, disinterested altruism¯ something that has no place in nature, something that has never existed before in the whole history 0f the world. We are built as gene machines and cultured as meme machines, but we have the power tO turn agarnst our creators. alone on can rebel against the tyranny 0f the selfish replicators.

召 4 ″ / ど 2 / 、励ど g ど〃ど ra 々 0 〃 147 relatedness is 50 per cent, whichever way round you Ok at it. TO illustrate what I mean, I am gomg tO repeat Alexander's words, Juvenile' and Other appropriate words but with parent', reversed. 'Suppose that a 第 4 尾〃ー has a gene which tends tO cause an ど 0 ど〃 distribution Of parental benefits. A gene which in this fashion improves an individual's fitness when it is a カ 4 尾〃ー could not fail tO have lowered its fitness more when it was a ノ〃ど〃 / な . therefore reach the opposite conclusion tO Alexander, namely that in any parent/offspring conflict, the child must win! Obviously something is wrong here. B0th arguments have been put t00 simply. The purpose Of my reverse quotation is not tO prove the opposite point t0 Alexander, but simply t0 show that you cannot argue in that kind Of artificially asymmetrical way. Both Alexander's argument, and my reversal 0f it, erred through 100king at things from the point 0f view 0f an 市朝ノ〃 4 / ーー in Alexander's case, the parent, in my case, the child. I believe this kind Of error is all t00 easy tO make when we use the technical term 、 fitness'. This is why I have avoided using the word in this book. There is really on い one entity whose point Of view matters ln evolution, and that entity is the selfish gene. Genes in Juvenile bodies will be selected for their ability t0 outsmart parental bodies; genes in parental bodies will be selected for their ability t0 outsmart the young. There is no paradox in the fact that the very same genes successively occupy a Juvenile bOdy and a parental body. Genes are selected for their ability t0 make the best use 0f the levers of power at their disposal: they will exploit their prac- tical opportunities. When a gene is sitting in a Juvenile bOdy its practical opportunitres will be different from when it IS sitting in a parental body. Therefore its optimum policy will be different in the tWO stages in its bOdy's life history. There is no reason tO SUppose, as Alexander does, that the later optimum policy should necessarily overrule the earlier. There IS another way Of putting the argument against Alexander. He is tacitly assumlng a false asymmetry between the parent/child relationship on the one hand, and the brother/sister relationship on the Other. You will remember that, according tO Trivers, the cost to a selfish child of grabbing more than his share, the reason why he only grabs up t0 a point, is the danger 0f loss of his brothers and sisters who each bear half his genes. But

6. Genesmanship WHAT is the selfish gene? lt is not just one single physical bit of DNA. Just as in the primeval soup, it is 4 ″鑽ゆ / な廰 of a particular bit of DNA, distributed throughout the world. If we allow our- selves the licence of talking about genes as if they had consclous alms, always reassurmg ourselves that we could translate our sloppy language back into respectable terms if we wanted to, we can ask the question, what is a single selfish gene trying to do? lt is trying tO get more numerous in the gene POOI. Basically it does this by helping to program the bodies in which it finds itself to suruve and tO reproduce. But now we are emphasizing that 'it' IS a distributed agency, existing ln many different individuals at once. The key point of this chapter is that a gene might be able to assist 2 / な 4 Of itself which are sitting in Other bOdies. If SO, this would appear as individual altruism but it would be brought about by gene selfishness. Consider the gene for being an albino in man. ln fact several genes exist which can give tO albinism, but I am talking about Just one Of them. lt is recessrve; that is, it has tO be present ln double dose in order for the person to be an albino. This is true Of about I ln 20 000 Of us. But it is 引 so present, in single dose, ln about I ln 70 Of us, and these individuals are not albinos. Since it is distributed in many individuals, a gene such as the albino gene could, in theory, assist its own survival in the gene POOI by programming its bOdies tO behave altruistically towards Other albino b()dies, S1nce these are known tO contain the same gene. The albino gene should be quite happy if some of the bodies which it inhabits die, provided that in doing so they help other bOdies containing the same gene tO survive. If the albino gene could make one Of its bOdies save the lives Of ten albino bodies, then even the death of the altruist is amply compensated by the lncreased numbers Of albino genes in the gene POOI. ShouId we then expect albinos to be especially nice to each

gene will spend approximately half its time sitting in male bodies' and the other half sitting in female bodies. Some gene effects show themselves only in bodies 0f one sex. These are called sex- limited gene effects. A gene controlling penis-length expresses this effect only in male bodies, but it is carried about in female bOdies t00 and may have some quite different effect on female b()dies. There is no reason why a man should not inherit a tend— ency t0 develop a long penis from his mother. ln whichever of the two sorts 0f body it finds itself, we can expect a gene tO make the best use Of the opportunities ()ffered by that sort of body. These opportunities may well differ according tO whether the bOdy is male or female. As a convenient approxi— matl()n, we can once assume that each individual bOdy iS a selfish machine, trying t0 do the best for all its genes. The best policy for such a selfish machine will often be one thing if it is male, and quite a different thing if it is female. For brevitY' we shall agaln use the convention 0f thinking 0f the individual as though it had a conscious purpose. As before, we shall hold in the back of our mind that this is just a figure 0f speech. A b0dY is really a machine blindly programmed by its selfish genes. Consider again the mated pair with which we began the chap- ter. Both partners, as selfish machines, want' sons and daughters in equal numbers. TO this extent they agree. Where they disagree IS in whO is going tO bear the brunt Of the cost Of rearing each one of those children. Each individual wants as many surviving chil- dren as possible. The less he or she is obliged t0 inves い n any one of those children, the more children he or she can have. The Obvious way tO achieve this desirable state Of affairs is tO induce your sexual partner tO lnvest more than his or her fair share Of resources ln each child, leaving you free tO have Other children with other partners. This would be a desirable strategy for either sex, but it is more difficult for the female tO achieve. Since she starts by investing more than the male, in the form Of her large' food-rich egg, a mother is already at the moment Of conception committed' t0 each child more deeply than the father is. She stands to IOse more if the child dies than the father does. More t0 the point, she would have t() invest more than the father / 〃ーんど 、 / / 〃な in order tO bring a new substitute child up tO the same level of development. If she tried the tactic ofleaving the father hold- 157

4 0 が 3 simply dO not make evolutionary sense. This brings me to the first point I want to make about what this bOOk is 〃 0 た I am not advocating a morality based on evolu- tion. I am saying how things have evolved. I am not saying how we humans morally ought t0 behave. I stress this, because I know I am in danger of being misunderstood by those people, all t00 numerous, whO cannot distinguish a statement Of belief in what is the case from an advocacy of what ought to be the case. My own feeling is that a human society based simply on the gene's law of unlversal ruthless selfishness would be a very nasty society in which to live. But unfortunately, however much we may deplore something, it does not stop it being true. This bOOk is mainly intended tO be interesting, but if you would extract a moral from lt, read it as a warning. Be warned that if you wish, as I dO, tO build a society in which individuals cooperate generously and unselfishly towards a common good, you can expect little help from biological nature. Let us try to な〃 c ん generosity and altruism, because we are born selfish. Let us understand what our own selfish genes are up tO, because we may then at least have the chance -tO upset their designs, something which no Other specres has ever aspired tO. As a corollary to these remarks about teaching, it is a fallacy— incidentally a very common one—to suppose that genetically inherited traits are by definition fixed and unmodifiable. Our genes may instruct us tO be selfish, but we are not necessarily compelled t0 obey them all our lives. lt may just be more difficult tO learn altruism than it would be if we were genetically pro— grammed tO be altruistic. Among animals, man IS uniquely dominated by culture, by influences learned and handed down. Some would say that culture IS SO lmportant that genes, whether selfish or not, are virtually irrelevant tO the understanding Of human nature. Others would disagree. lt all depends where you stand in the debate over nature versus nurture' as determmants of human attributes. This brings me to the second thing this book IS not: it IS not an advocacy Of one posltion or another in the nature/nurture controversy. Naturally I have an 0P1n10n on this, but I am not going to express lt, except insofar as it implicit in the view of culture which I shall present in the fin chapter. If genes really turn out tO be totally irrelevant tO the determinatlon