The Selfish Gene

Richard Dawkins

Summary: This book has changed my life. It made me realize that I am a machine for propagating DNA–a survival machine. Everything else is a by-product of evolution.

Score: 90 / 100

This book has changed my life. It made me realize that I am a machine for propagating DNA–a survival machine. Everything else is a by-product of evolution.

Often the most important contribution a scientist can make is to discover a new way of seeing old theories or facts.

Evolution is blind to the future.


They have come a long way, those replicators. Now they go by the name of genes, and we are their survival machines.

A given gene will have many different effects on quite different parts of the body. A given part of the body will be influenced by many genes, and the effect of any one gene depends on interaction with many others.

Every day he puts together three new trial crews, by random shuffling of the candidates for each position, and he makes the three crews race against each other. After some weeks of this it will start to emerge that the winning boat often tends to contain the same individual men. These are marked up as good oarsmen. Other individuals seem consistently to be found in slower crews, and these are eventually rejected.

the basic unit of natural selection is best regarded not as the species, nor as the population, nor even as the individual, but as some small unit of genetic material which it is convenient to label the gene.

No doubt some of your cousins and great-uncles died in childhood, but not a single one of your ancestors did. Ancestors just don’t die young!

more so than others, and that is all there is to it.

One gene maybe regarded as a unit that survives through a large number of successive individual bodies.

The shorter a genetic unit is, the longer-in generations-it is likely to live.

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.

one theory is that senility represents an accumulation of deleterious copying errors and other kinds of gene damage which occur during the individual’s lifetime.

obviously a late-acting lethal will be more stable in the gene pool than an early-acting lethal.

According to this theory then, senile decay is simply a by-product of the accumulation in the gene pool of late-acting lethal and semi-lethal genes, which have been allowed to slip through the net of natural selection simply because they are late-acting.

if we wanted to increase the human life span, there are two general ways in which we could do it. Firstly, we could ban reproduction before a certain age, say forty. After some centuries of this the minimum age limit would be raised to fifty, and so on. It is conceivable that human longevity could be pushed up to several centuries by this means.

(Incidentally, an embryo in her mother’s ‘womb’ may have an even smaller embryo inside her own womb.

There are even genes-called mutators-that manipulate the rates of copying-errors in other genes.

Plants have no need of the neurone, because they get their living without moving around, but it is found in the great majority of animal groups.

A for Andromeda by Fred Hoyle and John Elliot

Roger Payne has pointed out that the acoustics of the sea have certain peculiar properties, which mean that the exceedingly loud ‘song’ of some whales could theoretically be heard all the way round the world, provided the whales swim at a certain depth.

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.

high-stake players will on average end up poorer than low-stake players; and low-stake players poorer than those who do not gamble at all.

it is often possible to picture males as high-stake high-risk gamblers, and females as safe investors, especially in polygamous species in which males compete for females.

He found that all first-generation hybrid daughter hives were non-hygienic: the behaviour of their hygienic parent seemed to have been lost, although as things turned out the hygienic genes were still there but were recessive, like human genes for blue eyes. When Rothenbuhler ‘back-crossed’ first-generation hybrids with a pure hygienic strain (again of course using queens and drones), he obtained a most beautiful result. The daughter hives fell into three groups. One group showed perfect hygienic behaviour, a second showed no hygienic behaviour at all, and the third went half way. This last group uncapped the wax cells of diseased grubs, but they did not follow through and throw out the larvae. Rothenbuhler surmised that there might be two separate genes, one gene for uncapping, and one gene for throwing-out.

Rothenbuhler guessed that his experimental group of apparently totally non-hygienic bees might conceal a subgroup possessing the throwing-out gene, but unable to show it because they lacked the uncapping gene. He confirmed this most elegantly by removing caps himself. Sure enough, half of the apparently non-hygienic bees thereupon showed perfectly normal throwing-out behaviour.

An evolutionarily stable strategy or ESS is defined as a strategy which, if most members of a population adopt it, cannot be bettered by an alternative strategy.

An ESS is stable, not because it is particularly good for the individuals participating in it, but simply because it is immune to treachery from within.

it is vitally important in the war of attrition that individuals should give no inkling of when they are going to give up.

Mexican social spider, Oecobius civitas, by J. W. Burgess: ‘If a spider is disturbed and driven out of its retreat, it darts across the rock and, in the absence of a vacant crevice to hide in, may seek refuge in the hiding place of another spider of the same species. If the other spider is in residence when the intruder enters, it does not attack but darts out and seeks a new refuge of its own. Thus once the first spider is disturbed the process of sequential displacement from web to web may continue for several seconds, often causing a majority of the spiders in the aggregation to shift from their home refuge to an alien one (Social Spiders, Scientific American, March 1976).


Crickets do not recognize each other as individuals, but hens and monkeys do.

If a batch of hens who have never met before are introduced to each other, there is usually a great deal of fighting. After a time the fighting dies down.

look back on the invention of the ESS concept as one of the most important advances in evolutionary theory since Darwin.

Maynard Smith’s concept of the ESS will enable us, for the first time, to see clearly how a collection of independent selfish entities can come to resemble a single organized whole. I think this will be true not only of social organizations within species, but also of ’ecosystems’ and ‘communities’ consisting of many species. In the long term, I expect the ESS concept to revolutionize the science of ecology.

Genetically speaking, your first cousin is equivalent to a great grandchild. Similarly, you are just as likely to ’take after’ your uncle (relatedness = 1/4) as after your grandfather (relatedness = 1/4).

We can now see that parental care is just a special case of kin altruism. 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.


the case of bereaved monkey mothers who have been seen to steal a baby from another female, and look after it.

fundamental asymmetry in the parent/child relationship itself. Parents care more for their children than children do for their parents, although the genetic relationship is symmetrical, and certainty of relatedness is just as great both ways.

Caring can only be evolutionarily stable as part of a mixed strategy-at least some bearing has to go on.

Wild animals almost never die of old age: starvation, disease, or predators catch up with them long before they become really senile. Until recently this was true of man too.

Even in apparently faithful monogamous species, the female may be wedded to a male’s territory rather than to him personally.

Genes for having too many children are just not passed on to the next generation in large numbers, because few of the children bearing these genes reach adulthood.

But you cannot have an unnatural welfare state, unless you also have unnatural birth-control, otherwise the end result will be misery even greater than that which obtains in nature.

in one experiment mice were put in an outdoor enclosure with plenty of food, and allowed to breed freely. The population grew up to a point, then levelled off. The reason for the levelling-off turned out to be that the females became less fertile as a consequence of over-crowding: they had fewer babies.

Mother pigs do sometimes devour their young, but I do not know whether they pick especially on runts.

When a woman reached the age where the average chance of each child reaching adulthood was just less than half the chance of each grandchild of the same age reaching adulthood, any gene for investing in grandchildren in preference to children would tend to prosper. Such a gene is carried by only one in four grandchildren, whereas the rival gene is carried by one in two children, but the greater expectation of life of the grandchildren outweighs this, and the ‘grandchild altruism’ gene prevails in the gene pool.

Selfish greed seems to characterize much of child behaviour.

Wild birds can die after being starved for only a few hours.

An individual should reckon his own welfare as twice as valuable as that of his brothers, which is the basic assumption Trivers makes. But he should also value himself twice as highly as one of his own future children.

Signals like purring and smiling may have been selected because they enable parents to learn which of their actions are most beneficial to their children.

In frogs, for instance, neither sex has a penis.

label males as males, and females as females, throughout animals and plants. This is that the sex cells or ‘gametes’ of males are much smaller and more numerous than the gametes of females.

In the system known as isogamy the individuals are not distinguishable into two sexes. Anybody can mate with anybody else.

All eggs are capable of developing into either a male or a female. It is the sperms that carry the sex-determining chromosomes. Half the sperms produced by a man are female-producing, or X-sperms, and half are male-producing, or Y-sperms.

An individual cannot literally choose the sex of his children. But genes for tending to have children of one sex or the other are possible.

The strategy of producing equal numbers of sons and daughters is an evolutionarily stable strategy, in the sense that any gene for departing from it makes a net loss.

Some gene effects show themselves only in bodies of one sex. These are called sex-limited gene effects. A gene controlling penis-length expresses this effect only in male bodies, but it is carried about in female bodies too and may have some quite different effect on female bodies. There is no reason why a man should not inherit a tendency to develop a long penis from his mother.

male mice secrete a chemical which when smelt by a pregnant female can cause her to abort. She only aborts if the smell is different from that of her former mate. In this way. a male mouse destroys his potential step-children,

We shall see below a reason why a female might want a long ’engagement’ period before copulation. Here we have a reason why a male might want one too. Provided he can isolate her from all contact with other males, it helps to avoid being the unwitting benefactor of another male’s children.

she brings the dowry of a large, nutritious egg. A male who successfully copulates gains a valuable food reserve for his offspring.

There is a macabre sense in which the unfortunate male mantis can be said to invest in his children. He is used as food to help make the eggs which will then be fertilized, posthumously, by his own stored sperms.

The male is inevitably provided with an opportunity to take the prior decision to desert, closing the female’s options, and forcing her to decide whether to leave the young to certain death, or whether to stay with it and rear it. Therefore, maternal care is more common among land animals than paternal care.

A female who selects an old male is not necessarily going to have more descendants than a rival female who chooses a young one who shows some other evidence of good genes. What other evidence? There are many possibilities. Perhaps strong muscles as evidence of ability to catch food, perhaps long legs as evidence of ability to run away from predators.

Extravagances such as the tails of male birds of paradise may therefore have evolved by a kind of unstable, runaway process.

Darwin first proposed it, under the name of sexual selection.

Because of a fundamental difference between the size and numbers of sperms and eggs, males are in general likely to be biased towards promiscuity and lack of paternal care.

Then when the mule reaches adulthood it turns out to be sterile. This is presumably because, although horse chromosomes and donkey chromosomes are sufficiently similar to cooperate in the building of a good strong mule body, they are not similar enough to work together properly in meiosis.

The physical characteristics of the calls seem to be ideally shaped to be difficult to locate. If an acoustic engineer were asked to design a sound that a predator would find it hard to approach, he would produce something very like the real alarm calls of many small songbirds.

‘honey-pot’ ants there is a caste of workers with grotesquely swollen, food-packed abdomens, whose sole function in life is to hang motionless from the ceiling like bloated light-bulbs, being used as food stores by the other workers.

A society of ants, bees, or termites achieves a kind of individuality at a higher level.

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.

A hymenopteran nest typically has only one mature queen. She made one mating flight when young and stored up the sperms for the rest of her long life-ten years or even longer.

It follows that a hymenopteran female is more closely related to her full sisters than she is to her offspring of either sex.

If you are a hymenopteran female, the most efficient way for you to propagate your genes is to refrain from breeding yourself, and to make your mother provide you with reproductive sisters and brothers in the ratio 3:1.

True warfare in which large rival armies fight to the death is known only in man and in social insects.

parasol ants of South America.

It has been suggested that some aphids have evolved a backside that looks and feels like an ant’s face, the better to attract ants.

The mitochondria are chemical factories, responsible for providing most of the energy we need.

Recently it has been plausibly argued that mitochondria are, in origin, symbiotic bacteria who joined forces with our type of cell very early in evolution.

He concluded, as had Darwin, that delayed reciprocal altruism can evolve in species that are capable of recognizing and remembering each other as individuals.

in a population consisting largely of grudgers, neither cheat nor sucker will invade.

Mice kept in isolation tend to develop unpleasant sores on those parts of their heads that they cannot reach. In one study, mice kept in groups did not suffer in this way, because they licked each others’ heads.

Language seems to ’evolve’ by non-genetic means, and at a rate which is orders of magnitude faster than genetic evolution.

By comparing the songs of fathers and sons, Jenkins showed that song patterns were not inherited genetically. Each young male was likely to adopt songs from his territorial neighbours by imitation, in an analogous way to human language.

memes should be regarded as living structures, not just metaphorically but technically. When you plant a fertile meme in my mind you literally parasitize my brain, turning it into a vehicle for the meme’s propagation in just the way that a virus may parasitize the genetic mechanism of a host cell. And this isn’t just a way of talking-the meme for, say, “belief in life after death” is actually realized physically, millions of times over, as a structure in the nervous systems of individual men the world over.’

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.

For example, the habit of celibacy is presumably not inherited genetically. A gene for celibacy is doomed to failure in the gene pool, except under very special circumstances such as we find in the social insects.

Socrates may or may not have a gene or two alive in the world today, as G. C. Williams has remarked, but who cares? The meme-complexes of Socrates, Leonardo, Copernicus and Marconi are still going strong.

Axelrod translated all 15 strategies into one common programming language, and set them against one another in one big computer. (Sunday, August 12, 2012, 10:05 PM, page 3880)

simple Tit for Tat. Indeed the least successful of all the strategies (except Random) was the most elaborate. (Sunday, August 12, 2012, 10:15 PM, page 3928-29)

Significantly, the 8 top-scoring strategies were the very same 8 nice strategies, the 7 nasties trailing well behind. (Sunday, August 12, 2012, 10:16 PM, page 3935-36)

Boyd and Lorberbaum showed that a population of Tit for Tat could be invaded, evolutionarily speaking, by a mixture of Tit for Two Tats and Suspicious Tit for Tat, the two prospering in each other’s company. (Sunday, August 12, 2012, 10:35 PM, page 4030-32)

So even if Tit for Tat is rare in the population as a whole, it may still be locally common. In a local area, Tit for Tat individuals may meet each other often enough to prosper from mutual cooperation, even though calculations that take into account only the global frequency in the total population might suggest that they are below the ‘knife-edge’ critical frequency.

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.

Especially since I may fear that you are fearing that I. ..

Wilkinson found that those individuals who struck lucky on any one night did indeed sometimes donate blood, by regurgitation, to their less fortunate comrades.

Natural selection favours some genes rather than others not because of the nature of the genes themselves, but because of their consequences-their phenotypic effects.

Suppose it happened to bias meiosis in such a way that it, the mutant gene itself, was more likely than its allelic partner to end up in the egg. There are such genes and they are called segregation distorters.

One of the best-known segregation distorters is the so-called t gene in mice.

There is some evidence that wild populations of mice have, in the past, gone extinct through epidemics of t genes.

Admittedly, nobody has actually studied the genetics of caddis houses.

Although geneticists may think it an odd idea, it is therefore sensible for us to speak of genes ‘for’ stone shape, stone size, stone hardness and so on.

We are ready for the next step in the argument: genes in one organism can have extended phenotypic effects on the body of another organism.

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.

Millions of Nosema club together to mass-produce juvenile hormone in the beetle larva’s body, thereby preventing it from turning into an adult. Instead it goes on growing, ending up as a giant larva more than twice the weight of a normal adult.

we are all relics of ancient parasitic mergers.

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.

A plasmid is even smaller than a virus, and it normally consists of only a few genes.

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.

I do not know of any direct evidence that sexually transmitted diseases increase the libido of sufferers, but I conjecture that it would be worth looking into.

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.

The essential quality that an entity needs, if it is to become an effective gene vehicle, is this. It must have an impartial exit channel into the future, for all the genes inside it.

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.

published: 2012-08-29
last modified: 2023-11-19