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Notes

Here are some text that I highlighted in the book:

A central debate within Darwinism concerns the unit that is actually selected: what kind of entity is it that survives, or does not survive, as a consequence of natural selection. That unit will become, more or less by definition, ‘selfish’. Altruism might well be favoured at other levels. Does natural selection choose between species? If so, we might expect individual organisms to behave altruistically ‘for the good of the species’. They might limit their birth rates to avoid overpopulation, or restrain their hunting behaviour to conserve the species’ future stocks of prey. It was such widely disseminated misunderstandings of Darwinism that originally provoked me to write the book.
At no time does this evolution of the ‘cooperative gene’ violate the fundamental principle of the selfish gene.
Presumably there is indeed no purpose in the ultimate fate of the cosmos, but do any of us really tie our life’s hopes to the ultimate fate of the cosmos anyway? Of course we don’t; not if we are sane. Our lives are ruled by all sorts of closer, warmer, human ambitions and perceptions. To accuse science of robbing life of the warmth that makes it worth living is so preposterously mistaken, so diametrically opposite to my own feelings and those of most working scientists, I am almost driven to the despair of which I am wrongly suspected. A similar tendency to shoot the messenger is displayed by other critics who have objected to what they see as the disagreeable social, political or economic implications of The Selfish Gene.
One of the dominant messages of The Selfish Gene (reinforced by the title essay of A Devil’s Chaplain) is that we should not derive our values from Darwinism, unless it is with a negative sign. Our brains have evolved to the point where we are capable of rebelling against our selfish genes. The fact that we can do so is made obvious by our use of contraceptives. The same principle can and should work on a wider scale.
The selfish gene theory is Darwin’s theory, expressed in a way that Darwin did not choose but whose aptness, I should like to think, he would instantly have recognized and delighted in.
My point was that there are two ways of looking at natural selection, the gene’s angle and that of the individual. If properly understood they are equivalent; two views of the same truth. You can flip from one to the other and it will still be the same neo-Darwinism.
I shall argue that a predominant quality to be expected in a successful gene is ruthless selfishness. This gene selfishness will usually give rise to selfishness in individual behaviour. However, as we shall see, there are special circumstances in which a gene can achieve its own selfish goals best by fostering a limited form of altruism at the level of individual animals. ‘Special’ and ‘limited’ are important words in the last sentence. Much as we might wish to believe otherwise, universal love and the welfare of the species as a whole are concepts that simply do not make evolutionary sense.
Let us try to teach 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 that no other species has ever aspired to.
It often turns out on closer inspection that acts of apparent altruism are really selfishness in disguise. Once again, I do not mean that the underlying motives are secretly selfish, but that the real effects of the act on survival prospects are the reverse of what we originally thought.
Perhaps one reason for the great appeal of the group selection theory is that it is thoroughly in tune with the moral and political ideals that most of us share.
They have come a long way, those replicators. Now they go by the name of genes, and we are their survival machines.
This normal cell division is called mitosis. But there is another kind of cell division called meiosis. This occurs only in the production of the sex cells; the sperms or eggs. Sperms and eggs are unique among our cells in that, instead of containing 46 chromosomes, they contain only 23.
The process of swapping bits of chromosome is called crossing over. It is very important for the whole argument of this book. It means that if you got out your microscope and looked at the chromosomes in one of your own sperms (or eggs if you are female) it would be a waste of time trying to identify chromosomes that originally came from your father and chromosomes that originally came from your mother. (This is in marked contrast to the case of ordinary body cells (see page 31).) Any one chromosome in a sperm would be a patchwork, a mosaic of maternal genes and paternal genes.
A gene is defined as any portion of chromosomal material that potentially lasts for enough generations to serve as a unit of natural selection. In the words of the previous chapter, a gene is a replicator with high copying-fidelity.
Now comes the important point. The shorter a genetic unit is, the longer—in generations—it is likely to live. In particular, the less likely it is to be split by any one crossing-over.
The life-span of a chromosome is one generation.
The genes are the immortals, or rather, they are defined as genetic entities that come close to deserving the title. We, the individual survival machines in the world, can expect to live a few more decades. But the genes in the world have an expectation of life that must be measured not in decades but in thousands and millions of years.
A gene can live for a million years, but many new genes do not even make it past their first generation. The few new ones that succeed do so partly because they are lucky, but mainly because they have what it takes, and that means they are good at making survival machines.
Genes are competing directly with their alleles for survival, since their alleles in the gene pool are rivals for their slot on the chromosomes of future generations. Any gene that behaves in such a way as to increase its own survival chances in the gene pool at the expense of its alleles will, by definition, tautologously, tend to survive. The gene is the basic unit of selfishness.
As far as a gene is concerned, its alleles are its deadly rivals, but other genes are just a part of its environment, comparable to temperature, food, predators, or companions.
It is only on average that the best men tend to be in the winning boat.
a gene that is consistently on the losing side is not unlucky; it is a bad gene.
The true ‘purpose’ of DNA is to survive, no more and no less.
The reason why they cannot manipulate our puppet strings directly is the same: time-lags. Genes work by controlling protein synthesis. This is a powerful way of manipulating the world, but it is slow.
Polar bear genes can safely predict that the future of their unborn survival machine is going to be a cold one. They do not think of it as a prophecy, they do not think at all: they just build in a thick coat of hair, because that is what they have always done before in previous bodies, and that is why they still exist in the gene pool. They also predict that the ground is going to be snowy, and their prediction takes the form of making the coat of hair white and therefore camouflaged. If the climate of the Arctic changed so rapidly that the baby bear found itself born into a tropical desert, the predictions of the genes would be wrong, and they would pay the penalty. The young bear would die, and they inside it.
Some form of weighing up of the odds has to be done. But of course we do not have to think of the animals as making the calculations consciously. All we have to believe is that those individuals whose genes build brains in such a way that they tend to gamble correctly are as a direct result more likely to survive, and therefore to propagate those same genes.
One way for genes to solve the problem of making predictions in rather unpredictable environments is to build in a capacity for learning. Here the program may take the form of the following instructions to the survival machine: ‘Here is a list of things defined as rewarding: sweet taste in the mouth, orgasm, mild temperature, smiling child.
The possibilities of saccharine and masturbation are not anticipated according to this example; nor are the dangers of over-eating sugar in our environment where it exists in unnatural plenty.
Perhaps consciousness arises when the brain’s simulation of the world becomes so complete that it must include a model of itself.* Obviously the limbs and body of a survival machine must constitute an important part of its simulated world; presumably for the same kind of reason, the simulation itself could be regarded as part of the world to be simulated. Another word for this might indeed be ‘self-awareness’, but I don’t find this a fully satisfying explanation of the evolution of consciousness, and this is only partly because it involves an infinite regress—if there is a model of the model, why not a model of the model of the model …?
survival machines as executive decision-takers from their ultimate masters, the genes.
Genes are the primary policy-makers; brains are the executives.
It may well be that all animal communication contains an element of deception right from the start, because all animal interactions involve at least some conflict of interest.
To a survival machine, another survival machine (which is not its own child or another close relative) is part of its environment, like a rock or a river or a lump of food. It is something that gets in the way, or something that can be exploited. It differs from a rock or a river in one important respect: it is inclined to hit back. This is because it too is a machine that holds its immortal genes in trust for the future, and it too will stop at nothing to preserve them. Natural selection favours genes that control their survival machines in such a way that they make the best use of their environment. This includes making the best use of other survival machines, both of the same and of different species.
In a large and complex system of rivalries, removing one rival from the scene does not necessarily do any good: other rivals may be more likely to benefit from his death than oneself. This is the kind of hard lesson that has been learned by pest-control officers. You have a serious agricultural pest, you discover a good way to exterminate it and you gleefully do so, only to find that another pest benefits from the extermination even more than human agriculture does, and you end up worse off than you were before.
What if individuals retain some memory of the outcome of past fights? This depends on whether the memory is specific or general. Crickets have a general memory of what happened in past fights. A cricket that has recently won a large number of fights becomes more hawkish. A cricket that has recently had a losing streak becomes more dovish. This was neatly shown by R. D. Alexander. He used a model cricket to beat up real crickets. After this treatment the real crickets became more likely to lose fights against other real crickets. Each cricket can be thought of as constantly updating his own estimate of his fighting ability, relative to that of an average individual in his population. If animals such as crickets, who work with a general memory of past fights, are kept together in a closed group for a time, a kind of dominance hierarchy is likely to develop. An observer can rank the individuals in order. Individuals lower in the order tend to give in to individuals higher in the order. There is no need to suppose that the individuals recognize each other. All that happens is that individuals who are accustomed to winning become even more likely to win, while individuals who are accustomed to losing become steadily more likely to lose. Even if the individuals started by winning or losing entirely at random, they would tend to sort themselves out into a rank order. This incidentally has the effect that the number of serious fights in the group gradually dies down.
A good gene must be compatible with, and complementary to, the other genes with whom it has to share a long succession of bodies.
What is a single selfish gene trying to do? It is trying to get more numerous in the gene pool. Basically it does this by helping to program the bodies in which it finds itself to survive and to reproduce. But now we are emphasizing that ‘it’ is a distributed agency, existing in many different individuals at once. The key point of this chapter is that a gene might be able to assist replicas of itself that are sitting in other bodies. If so, this would appear as individual altruism but it would be brought about by gene selfishness.
Albino genes do not really ‘want’ to survive or to help other albino genes. But if the albino gene just happened to cause its bodies to behave altruistically towards other albinos, then automatically, willy-nilly, it would tend to become more numerous in the gene pool as a result. But, in order for this to happen, the gene would have to have two independent effects on bodies. Not only must it confer its usual effect of a very pale complexion. It must also confer a tendency to be selectively altruistic towards individuals with a very pale complexion. Such a double-effect gene could, if it existed, be very successful in the population.
The minimum requirement for a suicidal altruistic gene to be successful is that it should save more than two siblings (or children or parents), or more than four half-siblings (or uncles, aunts, nephews, nieces, grandparents, grandchildren), or more than eight first cousins, etc. Such a gene, on average, tends to live on in the bodies of enough individuals saved by the altruist to compensate for the death of the altruist itself.
Genetically speaking, an adult should devote just as much care and attention to its orphaned baby brother as it does to one of its own children. Its relatedness to both infants is exactly the same, . In gene selection terms, a gene for big sister altruistic behaviour should have just as good a chance of spreading through the population as a gene for parental altruism. In practice, this is an over-simplification for various reasons which we shall come to later, and brotherly or sisterly care is nothing like so common in nature as parental care. But the point I am making here is that there is nothing special genetically speaking about the parent/child relationship as against the brother/sister relationship. The fact that parents actually hand on genes to children, but sisters do not hand on genes to each other is irrelevant, since the sisters both receive identical replicas of the same genes from the same parents.
Grandparents and grandchildren have, genetically speaking, equal reason to behave altruistically to each other, since they share of each other’s genes. But if the grandchildren have the greater expectation of life, genes for grandparent to grandchild altruism have a higher selective advantage than genes for grandchild to grandparent altruism.
Fortunately, however, as Haldane well knew, it is not necessary to assume that survival machines do the sums consciously in their heads. Just as we may use a slide rule without appreciating that we are, in effect, using logarithms, so an animal may be pre-programmed in such a way that it behaves as if it had made a complicated calculation. This is not so difficult to imagine as it appears. When a man throws a ball high in the air and catches it again, he behaves as if he had solved a set of differential equations in predicting the trajectory of the ball. He may neither know nor care what a differential equation is, but this does not affect his skill with the ball. At some subconscious level, something functionally equivalent to the mathematical calculations is going on. Similarly, when a man takes a difficult decision, after weighing up all the pros and cons, and all the consequences of the decision that he can imagine, he is doing the functional equivalent of a large ‘weighted sum’ calculation, such as a computer might perform.
I have made the simplifying assumption that the individual animal works out what is best for his genes. What really happens is that the gene pool becomes filled with genes that influence bodies in such a way that they behave as if they had made such calculations.
Conceivably, racial prejudice could be interpreted as an irrational generalization of a kin-selected tendency to identify with individuals physically resembling oneself, and to be nasty to individuals different in appearance.
In most cases we should probably regard adoption, however touching it may seem, as a misfiring of a built-in rule. This is because the generous female is doing her own genes no good by caring for the orphan. She is wasting time and energy which she could be investing in the lives of her own kin, particularly future children of her own. It is presumably a mistake that happens too seldom for natural selection to have ‘bothered’ to change the rule by making the maternal instinct more selective. In many cases, by the way, such adoptions do not occur, and an orphan is left to die.
This is the case of bereaved monkey mothers who have been seen to steal a baby from another female, and look after it. I see this as a double mistake, since the adopter not only wastes her own time; she also releases a rival female from the burden of child-rearing, and frees her to have another child more quickly.
we should consider something like an index of ‘certainty’. Although the parent/child relationship is no closer genetically than the brother/sister relationship, its certainty is greater. It is normally possible to be much more certain who your children are than who your brothers are. And you can be more certain still who you yourself are!
If C is my identical twin, then I should care for him twice as much as I care for any of my children; indeed I should value his life no less than my own.* But can I be sure of him? He looks like me to be sure, but it could be that we just happen to share the genes for facial features. No, I will not give up my life for him, because although it is possible that he bears 100 per cent of my genes, I absolutely know that I contain 100 per cent of my genes, so I am worth more to me than he is.
She has a good chance of knowing for certain the bearers of her own genes. The poor father is much more vulnerable to deception. It is therefore to be expected that fathers will put less effort than mothers into caring for young.
Similarly, maternal grandmothers can be more sure of their grandchildren than paternal grandmothers can, and might be expected to show more altruism than paternal grandmothers. This is because they can be sure of their daughter’s children, but their son may have been cuckolded. Maternal grandfathers are just as sure of their grandchildren as paternal grandmothers are, since both can reckon on one generation of certainty and one generation of uncertainty. Similarly, uncles on the mother’s side should be more interested in the welfare of nephews and nieces than uncles on the father’s side, and in general should be just as altruistic as aunts are.
The truth is that all examples of child-protection and parental care, and all associated bodily organs, milk-secreting glands, kangaroo pouches, and so on, are examples of the working in nature of the kin selection principle.
According to Lack, therefore, individuals regulate their clutch size for reasons that are anything but altruistic. They are not practising birth control in order to avoid over-exploiting the group’s resources. They are practising birth control in order to maximize the number of surviving children they actually have, an aim which is the very opposite of that which we normally associate with birth control.
Obviously, if a female is presented with reliable evidence that a famine is to be expected, it is in her own selfish interests to reduce her own birth rate.
The reason why the fertility of males tails off gradually rather than abruptly is probably that males do not invest so much as females in each individual child anyway.
Have you ever heard a litter of piglets squealing to be first on the scene when the mother sow lies down to feed them? Or little boys fighting over the last slice of cake? Selfish greed seems to characterize much of child behaviour.
The loudness with which each baby screams is, ideally, proportional to how hungry he is. Therefore, if the parent always gives the food to the loudest screamer, they should all tend to get their fair share, since when one has had enough he will not scream so loudly. At least that is what would happen in the best of all possible worlds, if individuals did not cheat. But in the light of our selfish gene concept we must expect that individuals will cheat, will tell lies about how hungry they are. This will escalate, apparently rather pointlessly because it might seem that if they are all lying by screaming too loudly, this level of loudness will become the norm, and will cease, in effect, to be a lie. However, it cannot de-escalate, because any individual who takes the first step in decreasing the loudness of his scream will be penalized by being fed less, and is more likely to starve. Baby bird screams do not become infinitely loud, because of other considerations. For example, loud screams tend to attract predators, and they use up energy.
A child will lose no opportunity of cheating. It will pretend to be hungrier than it is, perhaps younger than it is, more in danger than it really is. It is too small and weak to bully its parents physically, but it uses every psychological weapon at its disposal: lying, cheating, deceiving, exploiting, right up to the point where it starts to penalize its relatives more than its genetic relatedness to them should allow.
This is that the ruthless behaviour of a baby cuckoo is only an extreme case of what must go on in any family. Full brothers are more closely related to each other than a baby cuckoo is to its foster brothers, but the difference is only a matter of degree. Even if we cannot believe that outright fratricide could evolve, there must be numerous lesser examples of selfishness where the cost to the child, in the form of losses to his brothers and sisters, is outweighed, more than two to one, by the benefit to himself. In such cases, as in the example of weaning time, there is a real conflict of interest between parent and child.
A gene that made a child grab more than his fair share when he was a child, at the expense of his parent’s total reproductive output, might indeed increase his chances of surviving. But he would pay the penalty when he came to be a parent himself, because his own children would tend to inherit the same selfish gene, and this would reduce his overall reproductive success. He would be hoist with his own petard. Therefore the gene cannot succeed, and parents must always win the conflict.
Once again I must emphasize that I am not talking about conscious motives. Nobody is suggesting that children deliberately and consciously deceive their parents because of the selfish genes within them. And I must repeat that when I say something like ‘A child should lose no opportunity of cheating … lying, deceiving, exploiting …’, I am using the word ‘should’ in a special way. I am not advocating this kind of behaviour as moral or desirable. I am simply saying that natural selection will tend to favour children who do act in this way, and that therefore when we look at wild populations we may expect to see cheating and selfishness within families. The phrase ‘the child should cheat’ means that genes that tend to make children cheat have an advantage in the gene pool. If there is a human moral to be drawn, it is that we must teach our children altruism, for we cannot expect it to be part of their biological nature.
Trivers has considered the possible courses of action open to a mother who has been deserted by her mate. Best of all for her would be to try to deceive another male into adopting her child, ‘thinking’ it is his own.
Natural selection would severely penalize such gullibility in males and indeed would favour males who took active steps to kill any potential step-children as soon as they mated with a new wife. This is very probably the explanation of the so-called Bruce effect: male mice secrete a chemical which when smelt by a pregnant female can cause her to abort.
Assuming then that a deserted female cannot fool a new male into adopting her child, what else can she do? Much may depend on how old the child is. If it is only just conceived, it is true that she has invested the whole of one egg in it and perhaps more, but it may still pay her to abort it and find a new mate as quickly as possible. In these circumstances it would be to the mutual advantage both of her and of the potential new husband that she should abort—since we are assuming she has no hope of fooling him into adopting the child. This could explain why the Bruce effect works from the female’s point of view. Another option open to a deserted female is to stick it out, and try and rear the child on her own. This will especially pay her if the child is already quite old. The older he is the more has already been invested in him, and the less it will take out of her to finish the job of rearing him. Even if he is still quite young, it might yet pay her to try to salvage something from her initial investment, even if she has to work twice as hard to feed the child, now that the male has gone. It is no comfort to her that the child contains half the male’s genes too, and that she could spite him by abandoning it. There is no point in spite for its own sake. The child carries half her genes, and the dilemma is now hers alone.
The unpleasant truth is that in some circumstances an advantage accrues to the partner who deserts first, whether it is the father or the mother. As Trivers puts it, the partner who is left behind is placed in a cruel bind.
My partner would “know” that if he/she left as well, the child would surely die. Therefore, assuming that my partner will take the decision that is best for his/her own selfish genes, I conclude that my own best course of action is to desert first.
One way for a female to do this is to play hard to get for a long time, to be coy. Any male who is not patient enough to wait until the female eventually consents to copulate is not likely to be a good bet as a faithful husband. By insisting on a long engagement period, a female weeds out casual suitors, and only finally copulates with a male who has proved his qualities of fidelity and perseverance in advance. Feminine coyness is in fact very common among animals, and so are prolonged courtship or engagement periods. As we have already seen, a long engagement can also benefit a male where there is a danger of his being duped into caring for another male’s child.
Could females force males to invest so heavily in their offspring before they allow copulation that it would no longer pay the males to desert after copulation? The idea is appealing. A male who waits for a coy female eventually to copulate with him is paying a cost: he is forgoing the chance to copulate with other females, and he is spending a lot of time and energy in courting her. By the time he is finally allowed to copulate with a particular female, he will inevitably be heavily ‘committed’ to her. There will be little temptation for him to desert her, if he knows that any future female he approaches will also procrastinate in the same manner before she will get down to business.
This is that a majority of the females can be relied upon to play the same game. If there are loose females in the population, prepared to welcome males who have deserted their wives, then it could pay a male to desert his wife, no matter how much he has already invested in her children.
Coy females will not copulate with a male until he has gone through a long and expensive courtship period lasting several weeks. Fast females will copulate immediately with anybody. Faithful males are prepared to go on courting for a long time, and after copulation they stay with the female and help her to rear the young. Philanderer males lose patience quickly if a female will not copulate with them straight away: they go off and look for another female; after copulation too they do not stay and act as good fathers, but go off in search of fresh females.
It is indeed the case that in many monogamous birds copulation does not take place until after the nest is built. The effect of this is that at the moment of conception the male has invested a good deal more in the child than just his cheap sperms. Demanding that a prospective mate should build a nest is one effective way for a female to trap him. It might be thought that almost anything that costs the male a great deal would do in theory, even if that cost is not directly paid in the form of benefit to the unborn children. If all females of a population forced males to do some difficult and costly deed, like slaying a dragon or climbing a mountain, before they would consent to copulate with them, they could in theory be reducing the temptation for the males to desert after copulation. Any male tempted to desert his mate and try to spread more of his genes by another female would be put off by the thought that he would have to kill another dragon.
There are therefore two conflicting selection pressures: predators tending to remove bright-colour genes from the gene pool, and sexual partners tending to remove genes for drabness. As in so many other cases, efficient survival machines can be regarded as a compromise between conflicting selection pressures. What interests us at the moment is that the optimal compromise for a male seems to be different from the optimal compromise for a female. This is of course fully compatible with our view of males as high-risk, high-reward gamblers.
A male on the other hand, who can produce millions of sperms every day, has everything to gain from as many promiscuous matings as he can snatch. Excess copulations may not actually cost a female much, other than a little lost time and energy, but they do not do her positive good. A male on the other hand can never get enough copulations with as many different females as possible: the word excess has no meaning for a male.
However, it is still possible that human males in general have a tendency towards promiscuity, and females a tendency towards monogamy, as we would predict on evolutionary grounds. Which of these two tendencies wins in particular societies depends on details of cultural circumstance, just as in different animal species it depends on ecological details.
Women paint their faces and glue on false eyelashes. Apart from special cases, like actors, men do not. Women seem to be interested in their own personal appearance and they are encouraged in this by their magazines and journals. Men’s magazines are less preoccupied with male sexual attractiveness, and a man who is unusually interested in his own dress and appearance is apt to arouse suspicion, both among men and among women. When a woman is described in conversation, it is quite likely that her sexual attractiveness, or lack of it, will be prominently mentioned. This is true, whether the speaker is a man or a woman. When a man is described, the adjectives used are much more likely to have nothing to do with sex.
Kamikaze behaviour and other forms of altruism and cooperation by workers are not astonishing once we accept the fact that they are sterile. The body of a normal animal is manipulated to ensure the survival of its genes both through bearing offspring and through caring for other individuals containing the same genes. Suicide in the interests of caring for other individuals is incompatible with future bearing of one’s own offspring. Suicidal self-sacrifice therefore seldom evolves. But a worker bee never bears offspring of its own. All its efforts are directed to preserving its genes by caring for relatives other than its own offspring. The death of a single sterile worker bee is no more serious to its genes than is the shedding of a leaf in autumn to the genes of a tree.
Cheats do better than indiscriminate altruists because they gain the benefits without paying the costs.
Fashions in dress and diet, ceremonies and customs, art and architecture, engineering and technology, all evolve in historical time in a way that looks like highly speeded up genetic evolution, but has really nothing to do with genetic evolution.
Just as genes propagate themselves in the gene pool by leaping from body to body via sperms or eggs, so memes propagate themselves in the meme pool by leaping from brain to brain via a process which, in the broad sense, can be called imitation.
The question really means: What is it about the idea of a god that gives it its stability and penetrance in the cultural environment? The survival value of the god meme in the meme pool results from its great psychological appeal. It provides a superficially plausible answer to deep and troubling questions about existence. It suggests that injustices in this world may be rectified in the next. The ‘everlasting arms’ hold out a cushion against our own inadequacies which, like a doctor’s placebo, is none the less effective for being imaginary. These are some of the reasons why the idea of God is copied so readily by successive generations of individual brains. God exists, if only in the form of a meme with high survival value, or infective power, in the environment provided by human culture.
‘genes are trying to increase their numbers in future gene pools’, what we really mean is ‘those genes that behave in such a way as to increase their numbers in future gene pools tend to be the genes whose effects we see in the world’
Another member of the religious meme complex is called faith. It means blind trust, in the absence of evidence, even in the teeth of evidence… Nothing is more lethal for certain kinds of meme than a tendency to look for evidence. The other apostles, whose faith was so strong that they did not need evidence, are held up to us as worthy of imitation. The meme for blind faith secures its own perpetuation by the simple unconscious expedient of discouraging rational inquiry.
When we die there are two things we can leave behind us: genes and memes.
is their rank order. The temptation to defect must be better than the reward for mutual cooperation, which must be better than the punishment for mutual defection, which must be better than the sucker’s pay-off. (Strictly speaking, there is one further condition for the game to qualify as a true Prisoner’s Dilemma: the average of the temptation and the sucker pay-offs must not exceed the reward. The reason for this additional condition will emerge later.)
The successive rounds of the game give us the opportunity to build up trust or mistrust, to reciprocate or placate, forgive or avenge. In an indefinitely long game, the important point is that we can both win at the expense of the banker, rather than at the expense of one another. After ten rounds of the game, I could theoretically have won as much as $5,000, but only if you have been extraordinarily silly (or saintly) and played cooperate every time, in spite of the fact that I was consistently defecting. More realistically, it is easy for each of us to pick up $3,000 of the banker’s money by both playing cooperate on all ten rounds of the game. For this we don’t have to be particularly saintly, because we can both see, from the other’s past moves, that the other is to be trusted. We can, in effect, police each other’s behaviour.
It was called Tit for Tat, and was submitted by Professor Anatol Rapoport, a well-known psychologist and games theorist from Toronto. Tit for Tat begins by cooperating on the first move and thereafter simply copies the previous move of the other player.
During these alternating runs both players receive on average 2.5 points per move (the average of 5 and 0). This is lower than the steady 3 points per move that both players can amass in a run of mutual cooperation (and, by the way, this is the reason for the ‘additional condition’ left unexplained on page 264).
A nice strategy is defined as one that is never the first to defect.
Another of Axelrod’s technical terms is ‘forgiving’. A forgiving strategy is one that, although it may retaliate, has a short memory. It is swift to overlook old misdeeds. Tit for Tat is a forgiving strategy. It raps a defector over the knuckles instantly but, after that, lets bygones be bygones. Chapter 10’s grudger is totally unforgiving. Its memory lasts the entire game. It never forgets a grudge against a player who has ever defected against it, even once. A strategy formally identical to Grudger was entered in Axelrod’s tournament under the name of Friedman, and it didn’t do particularly well. Of all the nice strategies (note that it is technically nice, although it is totally unforgiving), grudger/Friedman did next to worst. The reason unforgiving strategies don’t do very well is that they can’t break out of runs of mutual recrimination, even when their opponent is ‘remorseful’. It is possible to be even more forgiving than Tit for Tat. Tit for Two Tats allows its opponents two defections in a row before it eventually retaliates. This might seem excessively saintly and magnanimous. Nevertheless Axelrod worked out that, if only somebody had submitted Tit for Two Tats, it would have won the tournament. This is because it is so good at avoiding runs of mutual recrimination. So, we have identified two characteristics of winning strategies: niceness and forgivingness. This almost utopian-sounding conclusion—that niceness and forgivingness pay—came as a surprise to many of the experts, who had tried to be too cunning by submitting subtly nasty strategies; while even those who had submitted nice strategies had not dared anything so forgiving as Tit for Two Tats.
All but one of the top 15 strategies were nice, and all but one of the bottom 15 were nasty. But although the saintly Tit for Two Tats would have won the first tournament if it had been submitted, it did not win the second.
Axelrod’s name for a strategy that is good against a wide variety of other strategies is ‘robust’. Tit for Tat turned out to be a robust strategy. But the set of strategies that people happen to have submitted is an arbitrary set.
To say that Tit for Tat, say, is an ESS would be to say that Tit for Tat does well in a climate dominated by Tit for Tat. This could be seen as a special kind of ‘robustness’
. The only nasty strategy to survive beyond generation 200 was one called Harrington. Harrington’s fortunes rose steeply for about the first 150 generations.
A consequence of this indistinguishability is that, although Tit for Tat seems like an ESS, it is strictly not a true ESS. To be an ESS, remember, a strategy must not be invadable, when it is common, by a rare, mutant strategy. Now it is true that Tit for Tat cannot be invaded by any nasty strategy, but another nice strategy is a different matter. As we have just seen, in a population of nice strategies they will all look and behave exactly like one another: they will all cooperate all the time. So any other nice strategy, like the totally saintly Always Cooperate, although admittedly it will not enjoy a positive selective advantage over Tit for Tat, can nevertheless drift into the population without being noticed. So technically Tit for Tat is not an ESS.
But although Tit for Tat is strictly speaking not a true ESS, it is probably fair to treat some sort of mixture of basically nice but retaliatory ‘Tit for Tat-like’ strategies as roughly equivalent to an ESS in practice. Such a mixture might include a small admixture of nastiness. Robert Boyd and Jeffrey Lorberbaum, in one of the more interesting follow-ups to Axelrod’s work, looked at a mixture of Tit for Two Tats and a strategy called Suspicious Tit for Tat. Suspicious Tit for Tat is technically nasty, but it is not very nasty. It behaves just like Tit for Tat itself after the first move, but—this is what makes it technically nasty—it does defect on the very first move of the game.
Axelrod recognized that Tit for Tat is not strictly an ESS, and he therefore coined the phrase ‘collectively stable strategy’ to describe it. As in the case of true ESSs, it is possible for more than one strategy to be collectively stable at the same time. And again, it is a matter of luck which one comes to dominate a population. Always Defect is also stable, as well as Tit for Tat. In a population that has already come to be dominated by Always Defect, no other strategy does better. We can treat the system as bistable, with Always Defect being one of the stable points, Tit for Tat (or some mixture of mostly nice, retaliatory strategies) the other stable point. Whichever stable point comes to dominate the population first will tend to stay dominant.
Viscosity means any tendency for individuals to continue living close to the place where they were born.
Coming back to our knife-edge, then, Tit for Tat could surmount it. All that is required is a little local clustering, of a sort that will naturally tend to arise in natural populations. Tit for Tat has a built-in gift, even when rare, for crossing the knife-edge over to its own side. It is as though there were a secret passage underneath the knife-edge. But that secret passage contains a one-way valve: there is an asymmetry. Unlike Tit for Tat, Always Defect, though a true ESS, cannot use local clustering to cross the knife-edge. On the contrary. Local clusters of Always Defect individuals, far from prospering by each other’s presence, do especially badly in each other’s presence. Far from quietly helping one another at the expense of the banker, they do one another down. Always Defect, then, unlike Tit for Tat, gets no help from kinship or viscosity in the population. So, although Tit for Tat may be only dubiously an ESS, it has a sort of higher-order stability. What can this mean? Surely, stable is stable. Well, here we are taking a longer view. Always Defect resists invasion for a long time. But if we wait long enough, perhaps thousands of years, Tit for Tat will eventually muster the numbers required to tip it over the knife-edge, and the population will flip. But the reverse will not happen. Always Defect, as we have seen, cannot benefit from clustering, and so does not enjoy this higher-order stability. Tit for Tat, as we have seen, is ‘nice’, meaning never the first to defect, and ‘forgiving’, meaning that it has a short memory for past misdeeds. I now introduce another of Axelrod’s evocative technical terms. Tit for Tat is also ‘not envious’. To be envious, in Axelrod’s terminology, means to strive for more money than the other player, rather than for an absolutely large quantity of the banker’s money. To be non-envious means to be quite happy if the other player wins just as much money as you do, so long as you both thereby win more from the banker.
Sadly, however, when psychologists set up games of Iterated Prisoner’s Dilemma between real humans, nearly all players succumb to envy and therefore do relatively poorly in terms of money. It seems that many people, perhaps without even thinking about it, would rather do down the other player than cooperate with the other player to do down the banker. Axelrod’s work has shown what a mistake this is. It is only a mistake in certain kinds of game. Games theorists divide games into ‘zero sum’ and ‘nonzero sum’. A zero sum game is one in which a win for one player is a loss for the other. Chess is zero sum, because the aim of each player is to win, and this means to make the other player lose. Prisoner’s Dilemma, however, is a nonzero sum game. There is a banker paying out money, and it is possible for the two players to link arms and laugh all the way to the bank. This talk of laughing all the way to the bank reminds me of a delightful line from Shakespeare: The first thing we do, let’s kill all the lawyers.
Consider divorce. A good marriage is obviously a nonzero sum game, brimming with mutual cooperation. But even when it breaks down there are all sorts of reasons why a couple could benefit by continuing to cooperate, and treating their divorce, too, as nonzero sum. As if child welfare were not a sufficient reason, the fees of two lawyers will make a nasty dent in the family finances. So obviously a sensible and civilized couple begin by going together to see one lawyer, don’t they? Well, actually no. At least in England and, until recently, in all fifty states of the USA, the law, or more strictly—and significantly—the lawyers’ own professional code, doesn’t allow them to. Lawyers must accept only one member of a couple as a client. The other person is turned from the door, and either has no legal advice at all or is forced to go to another lawyer. And that is when the fun begins. In separate chambers but with one voice, the two lawyers immediately start referring to ‘us’ and ‘them’. ‘Us’, you understand, doesn’t mean me and my wife; it means me and my lawyer against her and her lawyer. When the case comes to court, it is actually listed as ‘Smith versus Smith’! It is assumed to be adversarial, whether the couple feel adversarial or not, whether or not they have specifically agreed that they want to be sensibly amicable. And who benefits from treating it as an ‘I win, you lose’ tussle? The chances are, only the lawyers.
The hapless couple have been dragged into a zero sum game. For the lawyers, however, the case of Smith v. Smith is a nice fat nonzero sum game, with the Smiths providing the pay-offs and the two professionals milking their clients’ joint account in elaborately coded cooperation. One way in which they cooperate is to make proposals that they both know the other side will not accept. This prompts a counter proposal that, again, both know is unacceptable. And so it goes on. Every letter, every telephone call exchanged between the cooperating ‘adversaries’ adds another wad to the bill. With luck, this procedure can be dragged out for months or even years, with costs mounting in parallel. The lawyers don’t get together to work all this out. On the contrary, it is ironically their scrupulous separateness that is the chief instrument of their cooperation at the expense of the clients. The lawyers may not even be aware of what they are doing. Like the vampire bats that we shall meet in a moment, they are playing to well-ritualized rules. The system works without any conscious overseeing or organizing. It is all geared to forcing us into zero sum games. Zero sum for the clients, but very much nonzero sum for the lawyers.
It is only fair to add that some lawyers play exactly the opposite role, persuading clients who are itching for a zero sum fight that they would do better to reach a nonzero sum settlement out of court.
Which aspects of human life foster ‘envy’, and which foster cooperation against a ‘banker’? Think, for instance, about wage-bargaining and ‘differentials’. When we negotiate our pay-rises, are we motivated by ‘envy’, or do we cooperate to maximize our real income? Do we assume, in real life as well as in psychological experiments, that we are playing a zero sum game when we are not?
‘Supporters who had been fierce rivals seconds before when Don Gillies fired in an 80th minute equaliser for Bristol, suddenly joined in a combined celebration. Referee Ron Challis watched helpless as the players pushed the ball around with little or no challenge to the man in possession.’ What had previously been a zero sum game had suddenly, because of a piece of news from the outside world, become a nonzero sum game. In the terms of our earlier discussion, it is as if an external ‘banker’ had magically appeared, making it possible for both Bristol and Coventry to benefit from the same outcome, a draw. Spectator sports like football are normally zero sum games for a good reason. It is more exciting for crowds to watch players striving mightily against one another than to watch them conniving amicably. But real life, both human life and plant and animal life, is not set up for the benefit of spectators. Many situations in real life are, as a matter of fact, equivalent to nonzero sum games. Nature often plays the role of ‘banker’, and individuals can therefore benefit from one another’s success. They do not have to do down rivals in order to benefit themselves. Without departing from the fundamental laws of the selfish gene, we can see how cooperation and mutual assistance can flourish even in a basically selfish world. We can see how, in Axelrod’s meaning of the term, nice guys may finish first.
Therefore the only rational strategy for either of us to play on the 100th round will be defect, and we can each assume that the other player will work that out and be fully resolved to defect on the last round. The last round can therefore be written off as predictable. But now the 99th round will be the equivalent of a one-off game, and the only rational choice for each player on this last but one game is also defect. The 98th round succumbs to the same reasoning, and so on back. Two strictly rational players, each of whom assumes that the other is strictly rational, can do nothing but defect if they both know how many rounds the game is destined to run. For this reason, when games theorists talk about the Iterated or Repeated Prisoner’s Dilemma game, they always assume that the end of the game is unpredictable, or known only to the banker.
The longer his estimate, the more he will play according to the mathematician’s expectations for the true iterated game: in other words, the nicer, more forgiving, less envious he will be. The shorter his estimate of the future of the game, the more he will be inclined to play according to the mathematician’s expectations for the one-off game: the nastier, and less forgiving will he be.
In the entrenched warfare of those times, the shadow of the future for each platoon was long. That is to say, each dug-in group of British soldiers could expect to be facing the same dug-in group of Germans for many months. Moreover, the ordinary soldiers never knew when, if ever, they were going to be moved; army orders are notoriously arbitrary, capricious, and incomprehensible to those receiving them. The shadow of the future was quite long enough, and indeterminate enough, to foster the development of a Tit for Tat type of cooperation. Provided, that is, that the situation was equivalent to a game of Prisoner’s Dilemma.
Mutual cooperation was undesirable from the generals’ point of view, because it wasn’t helping them to win the war. But it was highly desirable from the point of view of the individual soldiers on both sides. They didn’t want to be shot. Admittedly—and this takes care of the other pay-off conditions needed to make the situation a true Prisoner’s Dilemma—they probably agreed with the generals in preferring to win the war rather than lose it. But that is not the choice that faces an individual soldier. The outcome of the entire war is unlikely to be materially affected by what he, as an individual, does. Mutual cooperation with the particular enemy soldiers facing you across no man’s land most definitely does affect your own fate, and is greatly preferable to mutual defection, even though you might, for patriotic or disciplinary reasons, marginally prefer to defect (DC) if you could get away with it. It seems that the situation was a true Prisoner’s Dilemma. Something like Tit for Tat could be expected to grow up, and it did.
It is important, for any member of the Tit for Tat family of strategies, that the players are punished for defection. The threat of retaliation must always be there. Displays of retaliatory capability were a notable feature of the live-and-let-live system. Crack shots on both sides would display their deadly virtuosity by firing, not at enemy soldiers, but at inanimate targets close to the enemy soldiers, a technique also used in Western films (like shooting out candle flames). It does not seem ever to have been satisfactorily answered why the two first operational atomic bombs were used—against the strongly voiced wishes of the leading physicists responsible for developing them—to destroy two cities instead of being deployed in the equivalent of spectacularly shooting out candles.
‘goes well beyond a merely instrumental effort to prevent retaliation. It reflects moral regret for having violated a situation of trust, and it shows concern that someone might have been hurt.
Axelrod remarks that such ‘rituals of perfunctory and routine firing sent a double message. To the high command they conveyed aggression, but to the enemy they conveyed peace.’
A nice, forgiving, non-envious strategy could easily be programmed into a computer by a very nasty man. And vice versa. A strategy’s niceness is recognized by its behaviour, not by its motives (for it has none) nor by the personality of its author (who has faded into the background by the time the program is running in the computer). A computer program can behave in a strategic manner, without being aware of its strategy or, indeed, of anything at all.
Nobody would ever claim that a bacterium was a conscious strategist, yet bacterial parasites are probably engaged in ceaseless games of Prisoner’s Dilemma with their hosts and there is no reason why we should not attribute Axelrodian adjectives—forgiving, non-envious, and so on—to their strategies.
A doctor might say that the person’s ‘natural resistance’ is lowered by the injury. But perhaps the real reason is to do with games of Prisoner’s Dilemma. Do the bacteria, perhaps, have something to gain, but usually keep themselves in check? In the game between human and bacteria, the ‘shadow of the future’ is normally long since a typical human can be expected to live for years from any given starting-point. A seriously wounded human, on the other hand, may present a potentially much shorter shadow of the future to his bacterial guests. The ‘temptation to defect’ correspondingly starts to look like a more attractive option than the ‘reward for mutual cooperation’. Needless to say, there is no suggestion that the bacteria work all this out in their nasty little heads! Selection on generations of bacteria has presumably built into them an unconscious rule of thumb which works by purely biochemical means. Plants, according to Axelrod and Hamilton, may even take revenge, again obviously unconsciously.
It turns out in many cases that if a fig wasp entering a young fig does not pollinate enough flowers for seeds and instead lays eggs in almost all, the tree cuts off the developing fig at an early stage. All progeny of the wasp then perish.’
They form monogamous pairs and, within the pair, take turns to play the male and female roles.
In fact, what Fischer observed was that the fishes operate a system of pretty strict alternation. This is just what we should expect if they are playing Tit for Tat.
A question that sociologists and psychologists sometimes ask is why blood donors (in countries, such as Britain, where they are not paid) give blood. I find it hard to believe that the answer lies in reciprocity or disguised selfishness in any simple sense. It is not as though regular blood donors receive preferential treatment when they come to need a transfusion. They are not even issued with little gold stars to wear. Maybe I am naïve, but I find myself tempted to see it as a genuine case of pure, disinterested altruism. Be that as it may, blood-sharing in vampire bats seems to fit the Axelrod model well. We learn this from the work of G. S. Wilkinson.
Wilkinson found that those individuals who struck lucky on any one night did indeed sometimes donate blood, by regurgitation, to their less fortunate comrades.
This enabled him to cash out blood in the currency of hours of prolonged life.
although the act of donating blood would increase the chances of the donor dying, this increase was small compared with the increase in the recipient’s chances of surviving. Economically speaking, then, it seems plausible that vampire economics conform to the rules of a Prisoner’s Dilemma. The blood that the donor gives up is less precious to her (social groups in vampires are female groups) than the same quantity of blood is to the recipient.
Thirteen cases of donation were observed. In twelve out of these thirteen, the donor bat was an ‘old friend’ of the starved victim, taken from the same cave; in only one out of the thirteen cases was the starved victim fed by a ‘new friend’, not taken from the same cave. Of course this could be a coincidence but we can calculate the odds against this. They come to less than 1 in 500.
As for me, I am sceptical of all myths. If we want to know where the truth lies in particular cases, we have to look. What the Darwinian corpus gives us is not detailed expectations about particular organisms. It gives us something subtler and more valuable: understanding of principle. But if we must have myths, the real facts about vampires could tell a different moral tale. To the bats themselves, not only is blood thicker than water. They rise above the bonds of kinship, forming their own lasting ties of loyal blood-brotherhood. Vampires could form the vanguard of a comfortable new myth, a myth of sharing, mutualistic cooperation. They could herald the benignant idea that, even with selfish genes at the helm, nice guys can finish first.
On any sensible view of the matter Darwinian selection does not work on genes directly. DNA is cocooned in protein, swaddled in membranes, shielded from the world, and invisible to natural selection. If selection tried to choose DNA molecules directly it would hardly find any criterion by which to do so. All genes look alike, just as all recording tapes look alike. The important differences between genes emerge only in their effects.
The technical word phenotype is used for the bodily manifestation of a gene, the effect that a gene, in comparison with its alleles, has on the body, via development.
not because of the nature of the genes themselves, but because of their consequences—their phenotypic effects.
Here we are talking about single genes cheating against the other genes with which they share a body. The geneticist James Crow has called them ‘genes that beat the system’. One of the best-known segregation distorters is the so-called t gene in mice. When a mouse has two t genes it either dies young or is sterile. t is therefore said to be ‘lethal’ in the homozygous state. If a male mouse has only one t gene it will be a normal, healthy mouse except in one remarkable respect. If you examine such a male’s sperms you will find that up to 95 per cent of them contain the t gene, only 5 per cent the normal allele. This is obviously a gross distortion of the 50 per cent ratio that we expect. Whenever, in a wild population, a t allele happens to arise by mutation, it immediately spreads like a brushfire. How could it not, when it has such a huge unfair advantage in the meiotic lottery? It spreads so fast that, pretty soon, large numbers of individuals in the population inherit the t gene in double dose (that is, from both their parents). These individuals die or are sterile, and before long the whole local population is likely to be driven extinct. There is some evidence that wild populations of mice have, in the past, gone extinct through epidemics of t genes.
Natural selection (which, after all, works at the genic level) favours the segregation distorter, even though its effects at the level of the individual organism are likely to be bad.
The phenotypic effects of a gene are normally seen as all the effects that it has on the body in which it sits. This is the conventional definition. But we shall now see that the phenotypic effects of a gene need to be thought of as all the effects that it has on the world. It may be that a gene’s effects, as a matter of fact, turn out to be confined to the succession of bodies in which the gene sits. But, if so, it will be just as a matter of fact. It will not be something that ought to be part of our very definition. In all this, remember that the phenotypic effects of a gene are the tools by which it levers itself into the next generation. All that I am going to add is that the tools may reach outside the individual body wall. What might it mean in practice to speak of a gene as having an extended phenotypic effect on the world outside the body in which it sits? Examples that spring to mind are artefacts like beaver dams, bird nests, and caddis houses.
Having digressed so far, I cannot resist going a little further.
All that genes can really influence directly is protein synthesis. A gene’s influence upon a nervous system, or, for that matter, upon the colour of an eye or the wrinkliness of a pea, is always indirect. The gene determines a protein sequence that influences X that influences Y that influences Z that eventually influences the wrinkliness of the seed or the cellular wiring up of the nervous system.
It is as if the genes reached outside their ‘own’ body and manipulated the world outside. As in the case of the caddises, this language might make geneticists uneasy. They are accustomed to the effects of a gene being limited to the body in which it sits. But, again as in the case of the caddises, a close look at what geneticists ever mean by a gene having ‘effects’ shows that such uneasiness is misplaced. We need to accept only that the change in snail shell is a fluke adaptation. If it is, it has to have come about by Darwinian selection of fluke genes. We have demonstrated that the phenotypic effects of a gene can extend, not only to inanimate objects like stones, but to ‘other’ living bodies too.
Genes, then, reach outside their ‘own’ body to influence phenotypes in other bodies.
Look at what can happen when parasite genes and host genes do share a common exit. Wood-boring ambrosia beetles (of the species Xyleborus ferrugineus) are parasitized by bacteria that not only live in their host’s body but also use the host’s eggs as their transport into a new host. The genes of such parasites therefore stand to gain from almost exactly the same future circumstances as the genes of their host. The two sets of genes can be expected to ‘pull together’ for just the same reasons as all the genes of one individual organism normally pull together. It is irrelevant that some of them happen to be ‘beetle genes’, while others happen to be ‘bacterial genes’. Both sets of genes are ‘interested’ in beetle survival and the propagation of beetle eggs, because both ‘see’ beetle eggs as their passport to the future. So the bacterial genes share a common destiny with their host’s genes, and in my interpretation we should expect the bacteria to cooperate with their beetles in all aspects of life.
The key point, to repeat it, is that a parasite whose genes aspire to the same destiny as the genes of its host shares all the interests of its host and will eventually cease to act parasitically.
. Our own genes cooperate with one another, not because they are our own but because they share the same outlet—sperm or egg—into the future.
From some points of view it does not really matter whether these fragments originated as invading parasites or breakaway rebels. Their likely behaviour will be the same.
When we have a cold or a cough, we normally think of the symptoms as annoying byproducts of the virus’s activities. But in some cases it seems more probable that they are deliberately engineered by the virus to help it to travel from one host to another. Not content with simply being breathed into the atmosphere, the virus makes us sneeze or cough explosively. The rabies virus is transmitted in saliva when one animal bites another. In dogs, one of the symptoms of the disease is that normally peaceful and friendly animals become ferocious biters, foaming at the mouth. Ominously too, instead of staying within a mile or so of home like normal dogs, they turn into restless wanderers, propagating the virus far afield. It has even been suggested that the well-known hydrophobic symptom encourages the dog to shake the wet foam from its mouth—and with it the virus.
I am looking at a photograph of an adult dunnock, so small in comparison to its monstrous foster child that it has to perch on its back in order to feed it. Here we feel less sympathy for the host. We marvel at its stupidity, its gullibility. Surely any fool should be able to see that there is something wrong with a child like that.
They seem to act on the host’s nervous system in rather the same way as an addictive drug. This is not so hard to sympathize with, even for those with no experience of addictive drugs. A man can be aroused, even to erection, by a printed photograph of a woman’s body. He is not ‘fooled’ into thinking that the pattern of printing ink really is a woman. He knows that he is only looking at ink on paper, yet his nervous system responds to it in the same kind of way as it might respond to a real woman. We may find the attractions of a particular member of the opposite sex irresistible, even though the better judgment of our better self tells us that a liaison with that person is not in anyone’s long-term interests. The same can be true of the irresistible attractions of unhealthy food. The dunnock probably has no conscious awareness of its long-term best interests, so it is even easier to understand that its nervous system might find certain kinds of stimulation irresistible.
But there’s no doubt that if we do assume that the cuckoo’s gape is a powerful drug-like superstimulus, it becomes very much easier to explain what is going on. It becomes easier to sympathize with the behaviour of the diminutive parent standing on the back of its monstrous child. It is not being stupid. ‘Fooled’ is the wrong word to use. Its nervous system is being controlled, as irresistibly as if it were a helpless drug addict, or as if the cuckoo were a scientist plugging electrodes into its brain.
In the evolutionary ‘arms race’ between cuckoos and any host species, there is sort of built-in unfairness, resulting from unequal costs of failure. Each individual cuckoo nestling is descended from a long line of ancestral cuckoo nestlings, every single one of whom must have succeeded in manipulating its foster parent. Any cuckoo nestling that lost its hold, even momentarily, over its host would have died as a result. But each individual foster parent is descended from a long line of ancestors many of whom never encountered a cuckoo in their lives. And those that did have a cuckoo in their nest could have succumbed to it and still lived to rear another brood next season. The point is that there is an asymmetry in the cost of failure. Genes for failure to resist enslavement by cuckoos can easily be passed down the generations of robins or dunnocks. Genes for failure to enslave foster parents cannot be passed down the generations of cuckoos. This is what I meant by ‘built-in unfairness’, and by ‘asymmetry in the cost of failure’. The point is summed up in one of Aesop’s fables: ‘The rabbit runs faster than the fox, because the rabbit is running for his life while the fox is only running for his dinner.’ My colleague John Krebs and I have dubbed this the ‘life/dinner principle’.
Because of the life/dinner principle, animals might at times behave in ways that are not in their own best interests, manipulated by some other animal. Actually, in a sense they are acting in their own best interests: the whole point of the life/dinner principle is that they theoretically could resist manipulation but it would be too costly to do so. Perhaps to resist manipulation by a cuckoo you need bigger eyes or a bigger brain, which would have overhead costs. Rivals with a genetic tendency to resist manipulation would actually be less successful in passing on genes, because of the economic costs of resisting.
It floods the brain of the worker ant, grabs the reins of her muscles, woos her from deeply ingrained duties and turns her against her own mother. For ants, matricide is an act of special genetic madness and formidable indeed must be the drug that drives them to it. In the world of the extended phenotype, ask not how an animal’s behaviour benefits its genes; ask instead whose genes it is benefiting.
the caterpillar administers an aggression-arousing drug and it seems to slip them something addictively binding as well.
Natural selection favours those genes that manipulate the world to ensure their own propagation. This leads to what I have called the central theorem of the extended phenotype: An animal’s behaviour tends to maximize the survival of the genes ‘for’ that behaviour, whether or not those genes happen to be in the body of the particular animal performing it. I was writing in the context of animal behaviour, but the theorem could apply, of course, to colour, size, shape—to anything.
DNA molecules are replicators. They generally, for reasons that we shall come to, gang together into large communal survival machines or ‘vehicles’. The vehicles that we know best are individual bodies like our own. A body, then, is not a replicator; it is a vehicle. I must emphasize this, since the point has been misunderstood. Vehicles don’t replicate themselves; they work to propagate their replicators. Replicators don’t behave, don’t perceive the world, don’t catch prey or run away from predators; they make vehicles that do all those things. For many purposes it is convenient for biologists to focus their attention at the level of the vehicle. For other purposes it is convenient for them to focus their attention at the level of the replicator. Gene and individual organism are not rivals for the same starring role in the Darwinian drama. They are cast in different, complementary, and in many respects equally important roles, the role of replicator and the role of vehicle.
This is why—it is just another way of expressing the message of earlier chapters—the bee colony looks and behaves like a truly integrated single vehicle. Everywhere we find that life, as a matter of fact, is bundled into discrete, individually purposeful vehicles like wolves and bee-hives. But the doctrine of the extended phenotype has taught us that it needn’t have been so. Fundamentally, all that we have a right to expect from our theory is a battleground of replicators, jostling, jockeying, fighting for a future in the genetic hereafter. The weapons in the fight are phenotypic effects, initially direct chemical effects in cells but eventually feathers and fangs and even more remote effects.
I shall divide the question up into three. Why did genes gang up in cells? Why did cells gang up in many-celled bodies? And why did bodies adopt what I shall call a ‘bottlenecked’ life cycle? First then, why did genes gang up in cells? Why did those ancient replicators give up the cavalier freedom of the primeval soup and take to swarming in huge colonies? Why do they cooperate? We can see part of the answer by looking at how modern DNA molecules cooperate in the chemical factories that are living cells. DNA molecules make proteins. Proteins work as enzymes, catalysing particular chemical reactions. Often a single chemical reaction is not sufficient to synthesize a useful end-product
Tempting as it is, it is positively wrong to speak of the genes for the six enzymes of pathway 2 being selected ‘as a group’. Each one is selected as a separate selfish gene, but it flourishes only in the presence of the right set of other genes. Nowadays this cooperation between genes goes on within cells. It must have started as rudimentary cooperation between self-replicating molecules in the primeval soup (or whatever primeval medium there was). Cell walls perhaps arose as a device to keep useful chemicals together and stop them leaking away.
Large organisms can eat smaller ones, for instance, and can avoid being eaten by them.
Specialist cells serve other cells in the club and they also benefit from the efficiency of other specialists. If there are many cells, some can specialize as sensors to detect prey, others as nerves to pass on the message, others as stinging cells to paralyse the prey, muscle cells to move tentacles and catch the prey, secretory cells to dissolve it and yet others to absorb the juices. We must not forget that, at least in modern bodies like our own, the cells are a clone. All contain the same genes, although different genes will be turned on in the different specialist cells
the efforts of all those cells converge on the final goal of producing single cells again—sperms or eggs. The elephant not only has its beginning in a single cell, a fertilized egg. Its end, meaning its goal or end-product, is the production of single cells, fertilized eggs of the next generation. The life cycle of the broad and bulky elephant both begins and ends with a narrow bottleneck.
It will be helpful to imagine two hypothetical species of seaweed called bottle-wrack and splurge-weed. Splurge-weed grows as a set of straggling, amorphous branches in the sea. Every now and then branches break off and drift away. These breakages can occur anywhere in the plants, and the fragments can be large or small. As with cuttings in a garden, they are capable of growing just like the original plant. This shedding of parts is the species’s method of reproducing. As you will notice, it isn’t really different from its method of growing, except that the growing parts become physically detached from one another. Bottle-wrack looks the same and grows in the same straggly way. There is one crucial difference, however. It reproduces by releasing single-celled spores which drift off in the sea and grow into new plants. These spores are just cells of the plant like any others. As in the case of splurge-weed, no sex is involved. The daughters of a plant consist of cells that are clone-mates of the cells of the parent plant. The only difference between the two species is that splurge-weed reproduces by hiving off chunks of itself consisting of indeterminate numbers of cells, while bottle-wrack reproduces by hiving off chunks of itself always consisting of single cells.
Bottle-wrack reproduces by squeezing itself, every generation, through a single-celled bottleneck.
Bottle-wrack, on the other hand, makes a clear separation between growth and reproduction.
The complicated organs of an advanced animal like a human or a woodlouse have evolved by gradual degrees from the simpler organs of ancestors. But the ancestral organs did not literally change themselves into the descendant organs, like swords being beaten into ploughshares. Not only did they not. The point I want to make is that in most cases they could not. There is only a limited amount of change that can be achieved by direct transformation in the ‘swords to ploughshares’ manner. Really radical change can be achieved only by going ‘back to the drawing board’, throwing away the previous design and starting afresh. When engineers go back to the drawing board and create a new design, they do not necessarily throw away the ideas from the old design. But they don’t literally try to deform the old physical object into the new one. The old object is too weighed down with the clutter of history. Maybe you can beat a sword into a ploughshare, but try ‘beating’ a propellor engine into a jet engine! You can’t do it. You have to discard the propellor engine and go back to the drawing board.
So, the stereotyped growth cycle provides a clock, or calendar, by means of which embryological events may be triggered. Think of how readily we ourselves use the cycles of the earth’s daily rotation, and its yearly circumnavigation of the sun, to structure and order our lives. In the same way, the endlessly repeated growth rhythms imposed by a bottlenecked life cycle will—it seems almost inevitable—be used to order and structure embryology. Particular genes can be switched on and off at particular times because the bottleneck/growth-cycle calendar ensures that there is such a thing as a particular time. Such well-tempered regulations of gene activity are a prerequisite for the evolution of embryologies capable of crafting complex tissues and organs. The precision and complexity of an eagle’s eye or a swallow’s wing couldn’t emerge without clockwork rules for what is laid down when.
Evolution requires genetic change, mutation.
Mutation will make it unlikely that the cells within a plant are genetically identical, so they won’t collaborate wholeheartedly with one another in the manufacture of organs and new plants. Natural selection will choose among cells rather than ‘plants’. In bottle-wrack, on the other hand, all the cells within a plant are likely to have the same genes, because only very recent mutations could divide them. Therefore they will happily collaborate in manufacturing efficient survival machines.
To sum up, we have seen three reasons why a bottlenecked life history tends to foster the evolution of the organism as a discrete and unitary vehicle. The three may be labelled, respectively, ‘back to the drawing board’, ‘orderly timing-cycle’, and ‘cellular uniformity’
Let me end with a brief manifesto, a summary of the entire selfish gene/extended phenotype view of life. It is a view, I maintain, that applies to living things everywhere in the universe.
With only a little imagination we can see the gene as sitting at the centre of a radiating web of extended phenotypic power.
Scientists, unlike politicians, can take pleasure in being wrong.
The Cooperative Gene would have been an equally appropriate title for this book, and the book itself would not have changed at all. I suspect that a whole lot of mistaken criticisms could have been avoided.
it is zero for a random member of the background population with whom I might be competing. For purposes of theorizing about the evolution of altruism, r between first cousins is 0.125 only when compared to the reference background population (r = 0),
each gene has only one parent, one grandparent, one great grandparent, etc. I have one gene for blue eyes and the Queen has two.
Yan Wong, my co-author of The Ancestor’s Tale, from whom I learned everything I know about coalescence theory and much else besides, seized upon this and did the necessary Li/Durbin style calculations using my genome, and my genome alone, to make inferences about human history.
Henry Ford’s ‘History is more or less bunk’. But, religious answers apart (I am familiar with them; save your stamp), when you are actually challenged to think of pre-Darwinian answers to the questions ‘What is man?’ ‘Is there a meaning to life?’ ‘What are we for?’, can you, as a matter of fact, think of any that are not now worthless except for their (considerable) historic interest?
This error is easy to fall into if you think, as many people unaccountably seem to, that genetic ‘determination’ is for keeps—absolute and irreversible. In fact genes ‘determine’ behaviour only in a statistical sense (see also pp. 46–50)
Any weather forecast is subject to error. It is a statistical forecast only. We don’t see red sunsets as irrevocably determining fine weather the next day, and no more should we think of genes as irrevocably determining anything.
The Hebrew word in Isaiah is (almah), which undisputedly means ‘young woman’, with no implication of virginity. If ‘virgin’ had been intended, (bethulah) could have been used instead (the ambiguous English word ‘maiden’ illustrates how easy it can be to slide between the two meanings). The ‘mutation’ occurred when the pre-Christian Greek translation known as the Septuagint rendered almah into παϑθένος (parthenos), which really does usually mean virgin.
1920 when Karel Capek coined the word, ‘robots’ were mechanical beings that ended up with human feelings, like falling in love.
I think it is obvious what I meant by ‘created’, and it is very different from ‘control’. Anybody can see that, as a matter of fact, genes do not control their creations in the strong sense criticized as ‘determinism’. We effortlessly (well, fairly effortlessly) defy them every time we use contraception.
Expressions like ‘gene for long legs’ or ‘gene for altruistic behaviour’ are convenient figures of speech, but it is important to understand what they mean. There is no gene which single-handedly builds a leg, long or short. Building a leg is a multigene cooperative enterprise. Influences from the external environment too are indispensable; after all, legs are actually made of food! But there may well be a single gene which, other things being equal, tends to make legs longer than they would have been under the influence of the gene’s allele.
I use the term gene to mean ‘that which segregates and recombines with appreciable frequency.’ … A gene could be defined as any hereditary information for which there is a favorable or unfavorable selection bias equal to several or many times its rate of endogenous change.
I find his reasoning wrong but interesting, which, incidentally, he has been kind enough to tell me, is how he usually finds mine.
cuckoo eggs, after all, escape detection by looking exactly like host eggs.
Mary Midgley, which is typified by its first sentence: ‘Genes cannot be selfish or unselfish, any more than atoms can be jealous, elephants abstract or biscuits teleological.’ My own ‘In Defence of Selfish Genes’, in a subsequent issue of the same journal, is a full reply to this incidentally highly intemperate and vicious paper. It seems that some people, educationally over-endowed with the tools of philosophy, cannot resist poking in their scholarly apparatus where it isn’t helpful. I am reminded of P. B. Medawar’s remark about the attractions of ‘philosophy-fiction’ to ‘a large population of people, often with well-developed literary and scholarly tastes, who have been educated far beyond their capacity to undertake analytical thought’.
I have been an intensive programmer and user of a wide variety of digital computers for twenty-five years, and I can testify that using the Macintosh (or its imitators) is a qualitatively different experience from using any earlier type of computer. There is an effortless, natural feel to it, almost as if the virtual machine were an extension of one’s own body. To a remarkable extent the virtual machine allows you to use intuition instead of looking up the manual.
A serial computer is like a chess master ‘simultaneously’ playing twenty opponents but actually rotating around them. Unlike the chess master, the computer rotates so swiftly and quietly around its tasks that each human user has the illusion of enjoying the computer’s exclusive attention. Fundamentally, however, the computer is attending to its users serially.
so the whole supercomputer gets to the final answer orders of magnitude faster than a normal serial computer could. I said that an ordinary serial computer can create an illusion of being a parallel processor, by rotating its ‘attention’ sufficiently fast around a number of tasks. We could say that there is a virtual parallel processor sitting atop serial hardware. Dennett’s idea is that the human brain has done exactly the reverse. The hardware of the brain is fundamentally parallel, like that of the Edinburgh machine. And it runs software designed to create an illusion of serial processing: a serially processing virtual machine riding on top of parallel architecture. The salient feature of the subjective experience of thinking, Dennett thinks, is the serial ‘one-thing-after-another’, ‘Joycean’, stream of consciousness.
The psychologist Nicholas Humphrey, too, has developed a tempting hypothesis of how the evolution of a capacity to simulate might have led to consciousness. In his book, The Inner Eye, Humphrey makes a convincing case that highly social animals like us and chimpanzees have to become expert psychologists. Brains have to juggle with, and simulate, many aspects of the world. But most aspects of the world are pretty simple in comparison to brains themselves. A social animal lives in a world of others, a world of potential mates, rivals, partners, and enemies. To survive and prosper in such a world, you have to become good at predicting what these other individuals are going to do next. Predicting what is going to happen in the inanimate world is a piece of cake compared with predicting what is going to happen in the social world. Academic psychologists, working scientifically, aren’t really very good at predicting human behaviour. Social companions, using minute movements of the facial muscles and other subtle cues, are often astonishingly good at reading minds and second-guessing behaviour. Humphrey believes that this ‘natural psychological’ skill has become highly evolved in social animals, almost like an extra eye or other complicated organ. The ‘inner eye’ is the evolved social-psychological organ, just as the outer eye is the visual organ.
It will treat the squawking, gaping things in its parents’ nest—its younger brothers and sisters—as if they were squawking, gaping things in its own nest—its children. Far from being a brand new, complicated behavioural innovation, ‘fraternal behaviour’ would originally arise as a slight variant in the developmental timing of already-existing behaviour.
John Krebs and I have argued in two articles that most animal signals are best seen as neither informative nor deceptive, but rather as manipulative. A signal is a means by which one animal makes use of another animal’s muscle power. A nightingale’s song is not information, not even deceitful information. It is persuasive, hypnotic, spellbinding oratory.
is a strategy that does well against copies of itself. The rationale for this is as follows. A successful strategy is one that dominates the population. Therefore it will tend to encounter copies of itself.
They showed that the true ESS in this game is in fact a stable mixture of hawks and bullies.
If too much entering is going on in a population, available burrows become scarce, the chance of double-occupation goes up, and it therefore pays to dig. Conversely, if plenty of wasps are digging, the high availability of burrows favours entering. There is a critical frequency of entering in the population at which digging and entering are equally profitable. If the actual frequency is below the critical frequency, natural selection favours entering, because there is a good supply of available abandoned burrows. If the actual frequency is higher than the critical frequency, there is a shortage of available burrows and natural selection favours digging. So a balance is maintained in the population. The detailed, quantitative evidence suggests that this is a true mixed ESS, each individual wasp having a probability of digging or entering, rather than the population containing a mixture of digging and entering specialists.
He noticed that individual male butterflies in Wytham Wood, near Oxford, defended patches of sunlight. Females were attracted to sun patches, so a sun patch was a valuable resource, something worth fighting over. There were more males than sun patches and the surplus waited their chance in the leafy canopy. By catching males and releasing them one after the other, Davies showed that whichever of two individuals was released first into a sun patch was treated, by both individuals, as the ‘owner’. Whichever male arrived second in the sun patch was treated as the ‘intruder’. The intruder always, without exception, promptly conceded defeat, leaving the owner in sole control. In a final coup de grâce experiment, Davies managed to ‘fool’ both butterflies into ‘thinking’ that they were the owner and the other was the intruder. Only under these conditions did a really serious, prolonged fight break out. By the way, in all those cases where, for simplicity, I have spoken as though there was a single pair of butterflies there was really, of course, a statistical sample of pairs.
Now for the paradox. The labels ‘master’ and ‘slave’ turned out to be all topsy-turvy. Whenever a pair of pigs settled down to a stable pattern, the pig that ended up playing the ‘master’ or ‘exploiting’ role was the pig that, in all other ways, was subordinate. The so-called ‘slave’ pig, the one that did all the work, was the pig that was usually dominant. Anybody knowing the pigs would have predicted that, on the contrary, the dominant pig would have been the master, doing most of the eating; the subordinate pig should have been the hard-working and scarcely-eating slave. How could this paradoxical reversal arise? It is easy to understand, once you start thinking in terms of stable strategies. All that we have to do is scale the idea down from evolutionary time to developmental time, the time-scale on which a relationship between two individuals develops. The strategy ‘If dominant, sit by the food trough; if subordinate, work the lever’ sounds sensible, but would not be stable.
h its front feet firmly in the trough and impossible to dislodge. The subordinate pig would soon give up pressing the lever, for the habit would never be rewarded. But now consider the reverse strategy: ‘If dominant, work the lever; if subordinate, sit by the food trough.’ This would be stable, even though it has the paradoxical result that the subordinate pig gets most of the food. All that is necessary is that there should be some food left for the dominant pig when he charges up from the other end of the sty. As soon as he arrives, he has no difficulty in tossing the subordinate pig out of the trough.
He also showed that a male cricket is more likely to court females if he has recently won a fight against another male. This should be called the ‘Duke of Marlborough Effect’, after the following entry in the diary of the first Duchess of Marlborough: ‘His Grace returned from the wars today and pleasured me twice in his top-boots.’ An alternative name might be suggested by the following report from the magazine New Scientist about changes in levels of the masculine hormone testosterone: ‘Levels doubled in tennis players during the 24 hours before a big match. Afterwards, the levels in winners stayed up, but in losers they dropped.’
It is neglected no longer, and I can now take a more judicious and less evangelical view.
The answer is that brothers share of their genes over and above the 90 per cent (or whatever it is) that all individuals share in any case. There is a kind of baseline relatedness, shared by all members of a species; indeed, to a lesser extent, shared by members of other species. Altruism is expected towards individuals whose relatedness is higher than the baseline, whatever the baseline happens to be.
Why has natural selection favoured these genes, even though some of them end up in the bodies of sterile soldiers and are therefore not passed on? Because, thanks to the soldiers, copies of those very same genes have been saved in the bodies of the reproductive non-soldiers. The rationale is just the same as for all social insects (see Chapter 10), except that in other social insects, such as ants or termites, the genes in the sterile ‘altruists’ have only a statistical chance of helping copies of themselves in non-sterile reproductives. Aphid altruistic genes enjoy certainty rather than statistical likelihood since aphid soldiers are clone-mates of the reproductive sisters whom they benefit. In some respects Aoki’s aphids provide the neatest real-life illustration of the power of Hamilton’s ideas.
Kin selection follows from the fundamental assumptions of neo-Darwinism as night follows day.
A snail shell is an exquisite logarithmic spiral, but where does the snail keep its log tables; how indeed does it read them, since the lens in its eye lacks ‘linguistic support’ for calculating m, the coefficient of refraction? How do green plants ‘figure out’ the formula of chlorophyll?
The embryological development of any bit of an animal’s or plant’s body requires complicated mathematics for its complete description, but this does not mean that the animal or plant must itself be a clever mathematician! Very tall trees usually have huge buttresses flaring out like wings from the base of their trunks. Within any one species, the taller the tree, the relatively larger the buttresses. It is widely accepted that the shape and size of these buttresses are close to the economic optimum for keeping the tree erect, although an engineer would require quite sophisticated mathematics to demonstrate this. It would never occur to Sahlins or anyone else to doubt the theory underlying buttresses simply on the grounds that trees lack the mathematical expertise to do the calculations. Why, then, raise the problem for the special case of kin-selected behaviour? It can’t be because it is behaviour as opposed to anatomy, because there are plenty of other examples of behaviour (other than kin-selected behaviour, I mean) that Sahlins would cheerfully accept without raising his ‘epistemological’ objection; think, for instance, of my own illustration (pp. 124–5) of the complicated calculations that in some sense we all must do whenever we catch a ball. One cannot help wondering: are there social scientists who are quite happy with the theory of natural selection generally but who, for quite extraneous reasons that may have roots in the history of their subject, desperately want to find something—anything—wrong with the theory of kin selection specifically?
A lethal gene is one that kills its possessor. A recessive lethal, like any recessive gene, doesn’t exert its effect unless it is in double dose. Recessive lethals get by in the gene pool, because most individuals possessing them have only one copy and therefore never suffer the effects. Any given lethal is rare, because if it ever gets common it meets copies of itself and kills off its carriers.
But if a brother mates with a sister, or a father with a daughter, things are ominously different. However rare my lethal recessives may be in the population at large, and however rare my sister’s lethal recessives may be in the population at large, there is a disquietingly high chance that hers and mine are the same. If you do the sums, it turns out that, for every lethal recessive that I possess, if I mate with my sister one in eight of our offspring will be born dead or will die young. Incidentally, dying in adolescence is even more ‘lethal’, genetically speaking, than dying at birth: a stillborn child doesn’t waste so much of the parents’ vital time and energy. But, whichever way you look at it, close incest is not just mildly deleterious. It is potentially catastrophic. Selection for active incest-avoidance could be as strong as any selection pressure that has been measured in nature.
‘If Darwinian selection had really built into us an instinctive revulsion against incest, we wouldn’t need to forbid it. The taboo only grows up because people have incestuous lusts. So the rule against incest cannot have a “biological” function, it must be purely “social”.’ This objection is rather like the following: ‘Cars don’t need locks on the ignition switch because they have locks on the doors. Therefore ignition locks cannot be anti-theft devices; they must have some purely ritual significance!’
Too-distant outbreeding can also be bad because of genetic incompatibilities between different strains.
Quail, then, seem to avoid incest by their own internal lack of desire for those with whom they have grown up. Other animals do it by observing social laws, socially imposed rules of dispersal. Adolescent male lions, for instance, are driven out of the parental pride where female relatives remain to tempt them, and breed only if they manage to usurp another pride. In chimpanzee and gorilla societies it tends to be the young females who leave to seek mates in other bands. Both dispersal patterns, as well as the quail’s system, are to be found among the various cultures of our own species.
I recommend Alan Grafen’s essay ‘Natural Selection, Kin Selection and Group Selection’ as a clear-thinking, and I hope now definitive, sorting out of the neo-group-selection problem.
an old mother to succeed in manipulating her young adult daughter into staying and helping. The mother has everything to gain, while the daughter herself will have no inducement to resist her mother’s manipulation because she is genetically indifferent between the available choices.
Two books that go more thoroughly into the evolution of human sex differences are Martin Daly and Margo Wilson’s Sex, Evolution, and Behavior, and Donald Symons’s The Evolution of Human Sexuality.
be even less. Therefore an A has even more to gain by putting its effort into fighting, even less to gain by putting its effort into caring. Exactly the opposite will be true of the Bs as the generations go by. The key idea here is that a small initial difference between the sexes can be self-enhancing: selection can start with an initial, slight difference and make it grow larger and larger, until the As become what we now call males, the Bs what we now call females. The initial difference can be small enough to arise at random. After all, the starting conditions of the two sexes are unlikely to be exactly identical.
Starting from this minimal assumption, we positively expect that, however equal the two sexes may be at the start, they will diverge into two sexes specializing in opposite and complementary reproductive techniques. The separation between sperms and eggs is a symptom of this more general separation, not the cause of it.
guard and desert, which can be adopted by either sex. As in my ‘coy/fast and faithful/philanderer’ model, the interesting question is: what combinations of strategies among males are stable against what combinations of strategies among females? The answer depends upon our assumption about the particular economic circumstances of the species. Interestingly, though, however much we vary the economic assumptions, we don’t have a whole continuum of quantitatively varying stable outcomes. The model tends to home in one of only four stable outcomes. The four outcomes are named after animal species that exemplify them. There is the Duck (male deserts, female guards), the Stickleback (female deserts, male guards), the Fruit-fly (both desert), and the Gibbon (both guard).
What is especially interesting is that particular pairs, as opposed to other pairs, of these outcomes are jointly stable under the same economic circumstances. For instance, under one range of circumstances, both Duck and Stickleback are stable. Which of the two actually arises depends upon luck or, more precisely, upon accidents of evolutionary history
you get an endlessly repeating cycle. Ironically, this is precisely the cycle that I described hypothetically on pages 197–8, but I thought that I was doing it purely as an explanatory device, just as I had with hawks and doves. By analogy with hawks and doves I assumed, quite wrongly, that the cycle was hypothetical only, and that the system would really settle into a stable equilibrium. Schuster and Sigmund’s parting-shot leaves no more to be said: Briefly, then, we can draw two conclusions: (a) that the battle of sexes has much in common with predation; and (b) that the behaviour of lovers is oscillating like the moon, and unpredictable as the weather. Of course, people didn’t need differential equations to notice this before.
By breeding only from those with the longest ears you’ll succeed in increasing the average in later generations. For a while. But if you continue to breed from those with the longest ears there will come a time when the necessary variation is no longer available. They’ll all have the ‘longest’ ears, and evolution will grind to a halt. In normal evolution this sort of thing is not a problem, because most environments don’t carry on exerting consistent and unswerving pressure in one direction. The ‘best’ length for any particular bit of an animal will normally not be ‘a bit longer than the present average, whatever the present average may be’. The best length is more likely to be a fixed quantity, say three inches. But sexual selection really can have the embarrassing property of chasing an ever-driving ‘optimum’. Female fashion really could desire ever longer male ears, no matter how long the ears of the current population might already be. So variation really could seriously run out. And yet sexual selection does seem to have worked; we do see absurdly exaggerated male ornaments. We seem to have a paradox, which we may call the paradox of the vanishing variation.
First, a theory about why humans have lost the penis bone. An erect human penis can be so hard and stiff that people jokingly express scepticism that there is no bone inside. As a matter of fact lots of mammals do have a stiffening bone, the baculum or os penis, to help the erection along. What’s more, it is common among our relatives the primates; even our closest cousin the chimpanzee has one, although admittedly a very tiny one which may be on its evolutionary way out. There seems to have been a tendency to reduce the os penis in the primates; our species, along with a couple of monkey species, has lost it completely. So, we have got rid of the bone that in our ancestors presumably made it easy to have a nice stiff penis. Instead, we rely entirely on a hydraulic pumping system, which one cannot but feel is a costly and roundabout way of doing things. And, notoriously, erection can fail—unfortunate, to say the least, for the genetic success of a male in the wild.
But erection failure is a known early warning of diabetes and certain neurological diseases. Far more commonly it results from psychological factors—depression, anxiety, stress, overwork, loss of confidence and all that. (In nature, one might imagine males low in the ‘peck order’ being afflicted in this way. Some monkeys use the erect penis as a threat signal.) It is not implausible that, with natural selection refining their diagnostic skills, females could glean all sorts of clues about a male’s health, and the robustness of his ability to cope with stress, from the tone and bearing of his penis. But a bone would get in the way! Anybody can grow a bone in the penis; you don’t have to be particularly healthy or tough. So selection pressure from females forced males to lose the os penis, because then only genuinely healthy or strong males could present a really stiff erection and the females could make an unobstructed diagnosis.
Now to the ‘stethoscope’. Consider another notorious problem of the bedroom, snoring.
The hydraulic advertisement gains its effectiveness precisely because erection sometimes fails.
These can be called the Qualifying Handicap (any male who has survived in spite of his handicap must be pretty good in other respects, so females choose him); the Revealing Handicap (males perform some onerous task in order to expose their otherwise concealed abilities); the Conditional Handicap (only high-quality males develop a handicap at all); and finally Grafen’s preferred interpretation, which he calls the Strategic Choice Handicap (males have private information about their own quality, denied to females, and use this information to ‘decide’ whether to grow a handicap and how large it should be). Grafen’s Strategic Choice Handicap interpretation lends itself to ESS analysis. There is no prior assumption that the advertisements that males adopt will be costly or handicapping. On the contrary, they are free to evolve any kind of advertisement, honest or dishonest, costly or cheap. But Grafen shows that, given this freedom to start with, a handicap system would be likely to emerge as evolutionarily stable.
Females cannot perceive male quality directly but have to rely upon male advertising. At this stage we make no assumption about whether the advertisements are honest. Honesty is something else that may or may not emerge from the model; again that is what the model is for.
So, to the big question. Does Grafen’s ESS constitute the kind of world that Zahavi would recognize as a world of handicaps and honesty? The answer is yes. Grafen found that there can indeed be an evolutionarily stable world that combines the following Zahavian properties: 1. Despite having a free strategic choice of advertising level, males choose a level that correctly displays their true quality, even if this amounts to betraying that their true quality is low. At ESS, in other words, males are honest. 2. Despite having a free strategic choice of response to male advertisement, females end up choosing the strategy ‘Believe the males’. At ESS, females are justifiably ‘trusting’. 3. Advertising is costly. In other words, if we could somehow ignore the effects of quality and attractiveness, a male would be better off not advertising (thereby saving energy or being less conspicuous to predators). Not only is advertising costly; it is because of its costliness that a given advertising system is chosen. An advertising system is chosen precisely because it actually has the effect of reducing the success of the advertiser—all other things being held equal. 4. Advertising is more costly to worse males. The same level of advertising increases the risk for a puny male more than for a strong male. Low-quality males incur a more serious risk from costly advertising than high-quality males.
If Grafen is correct—and I think he is—it is a result of considerable importance for the whole study of animal signals. It might even necessitate a radical change in our entire outlook on the evolution of behaviour, a radical change in our view of many of the issues discussed in this book. Sexual advertisement is only one kind of advertisement. The Zahavi–Grafen theory, if true, will turn topsy-turvy biologists’ ideas of relations between rivals of the same sex, between parents and offspring, between enemies of different species.
if the queen is removed some previously sterile females start to come into breeding condition and then fight each other for the position of queen.
Mole rats are homocoprophagous, which is a polite way of saying that they eat one another’s faeces (not exclusively: that would run foul of the laws of the universe). Perhaps the large individuals perform a valuable role by storing up their faeces in the body when food is plentiful, so that they can act as an emergency larder when food is scarce—a sort of constipated commissariat.
The essential feature of haplodiploid animals, from the point of view of social evolution, is that an individual can be genetically closer to her sibling than to her offspring. This predisposes her to stay behind in the parental nest and rear siblings rather than leaving the nest to bear and rear her own offspring. Hamilton thought of a reason why, in termites too, siblings might be genetically closer to each other than parents are to offspring.
From our present point of view, the important consequence is that during this stage of the development of a termite colony, an individual is typically closer, genetically, to its siblings than to its potential offspring. And this, as we saw in the case of the haplodiploid hymenoptera, is a likely precondition for the evolution of altruistically sterile worker castes.
‘helping at the nest’. In many species of birds and mammals, young adults, before moving out to start families of their own, remain with their parents for a season or two and help to rear their younger brothers and sisters.
To use the ‘bearing and caring’ terminology of Chapter 7, somebody has to do some bearing; otherwise, there would be no young to care for! The point here is not that ‘otherwise, the species would go extinct’. Rather, in any population dominated by genes for pure caring, genes for bearing will tend to have an advantage. In social insects the bearer role is filled by the queens and males. They are the ones that go out into the world, looking for new ‘hollow trees’, and that is why they are winged, even in ants, whose workers are wingless. These reproductive castes are specialized for their whole lifetime. Birds and mammals that help at the nest do it the other way. Each individual spends part of its life (usually its first adult season or two) as a ‘worker’, helping to rear younger brothers and sisters, while for the remaining part of its life it aspires to be a ‘reproductive’.
My wager that all life, everywhere in the universe, would turn out to have evolved by Darwinian means has now been spelled out and justified more fully in my paper ‘Universal Darwinism’ and in the last chapter of The Blind Watchmaker.
The word meme seems to be turning out to be a good meme.
that carry them around and work to favour their continued replication. The first ten chapters of The Selfish Gene had concentrated exclusively on one kind of replicator, the gene. In discussing memes in the final chapter I was trying to make the case for replicators in general, and to show that genes were not the only members of that important class. Whether the milieu of human culture really does have what it takes to get a form of Darwinism going, I am not sure. But in any case that question is subsidiary to my concern. Chapter 11 will have succeeded if the reader closes the book with the feeling that DNA molecules are not the only entities that might form the basis for Darwinian evolution. My purpose was to cut the gene down to size, rather than to sculpt a grand theory of human culture.
DNA is a self-replicating piece of hardware.
f auld lang syne’, whereas Burns actually wrote ‘For auld lang syne’. A memically minded Darwinian immediately wonders what has been the ‘survival value’ of the interpolated phrase, ‘the sake of’. Remember that we are not looking for ways in which people might have survived better through singing the song in altered form. We are looking for ways in which the alteration itself might have been good at surviving in the meme pool. Everybody learns the song in childhood, not through reading Burns but through hearing it sung on New Year’s Eve. Once upon a time, presumably, everybody sang the correct words. ‘For the sake of’ must have arisen as a rare mutation. Our question is: why has the initially rare mutation spread so insidiously that it has become the norm in the meme pool? I don’t think the answer is far to seek. The sibilant ‘s’ is notoriously obtrusive. Church choirs are drilled to pronounce ‘s’ sounds as lightly as possible, otherwise the whole church echoes with hissing. A murmuring priest at the altar of a great cathedral can sometimes be heard, from the back of the nave, only as a sporadic sussuration of ‘s’s. The other consonant in ‘sake’, ‘k’, is almost as penetrating. Imagine that nineteen people are correctly singing ‘For auld lang syne’ and one person, somewhere in the room, slips in the erroneous ‘For the sake of auld lang syne’. A child, hearing the song for the first time, is eager to join in but uncertain of the words. Although almost everybody is singing ‘For auld lang syne’, the hiss of an ‘s’ and the cut of a ‘k’ force their way into the child’s ears, and when the refrain comes round again he too sings ‘For the sake of auld lang syne’.
University appointments committees have picked up the habit of using it as a rough and ready (too rough and too ready) way of comparing the scientific achievements of applicants for jobs.
If my exponential interpretation is accepted, what we are dealing with is a single slow-burning explosion of interest, running right through from 1967 to the late 1980s. Individual books and papers should be seen both as symptoms and as causes of this long-term trend.
R. A. Fisher’s most famous book is called The Genetical Theory of Natural Selection. Such a household name has this title become in the world of evolutionary biologists, it is hard for us to hear its first two words without automatically adding the third. I suspect that both Wilson and I must have done just that. This is a happy conclusion for all concerned, since nobody minds admitting to being influenced by Fisher!
Epidemics of ‘viruses’ and ‘worms’, deliberately released by malicious programmers, are now familiar hazards to computer-users all over the world.
I appeal to them: do you really want to pave the way for a new fat-cat profession? If not, stop playing at silly memes, and put your modest programming talents to better use.
I have had the predictable spate of letters from faith’s victims, protesting about my criticisms of it. Faith is such a successful brainwasher in its own favour, especially a brainwasher of children, that it is hard to break its hold. But what, after all, is faith? It is a state of mind that leads people to believe something—it doesn’t matter what—in the total absence of supporting evidence. If there were good supporting evidence then faith would be superfluous, for the evidence would compel us to believe it anyway. It is this that makes the often-parroted claim that ‘evolution itself is a matter of faith’ so silly. People believe in evolution not because they arbitrarily want to believe it but because of overwhelming, publicly available evidence.
Douglas Adams’s delightful Dirk Gently’s Holistic Detective Agency
Faith cannot move mountains (though generations of children are solemnly told the contrary and believe it). But it is capable of driving people to such dangerous folly that faith seems to me to qualify as a kind of mental illness. It leads people to believe in whatever it is so strongly that in extreme cases they are prepared to kill and to die for it without the need for further justification. Keith Henson has coined the name ‘memeoids’ for ‘victims that have been taken over by a meme to the extent that their own survival becomes inconsequential …

Cheng Nie

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