The Extended Phenotype: The Long Reach of the Gene

by Richard Dawkins

Are there important facts about life that we hardly notice simply because we lack the imagination to visualise alternatives which, like Fisher’s three sexes, might have existed in some possible world? I shall try to show that the answer is yes.

The author is trying to say that there may be different ways of perceiving things but those ways may not be so obvious

manipulate the world and shape it to assist their replication. It happens that they have ‘chosen’ to do so largely by moulding matter into large multicellular chunks which we call organisms, but this might not have been so. Fundamentally, what is going on is that replicating molecules ensure their survival by means of phenotypic effects on the world. It is only incidentally true that those phenotypic effects happen to be packaged up into units called individual organisms.

The selfish organism, and the selfish gene with its extended phenotype, are two views of the same Necker Cube.

we should ask why genes chose to group themselves together in nuclei, and in organisms.

Wilson’s (1978) On Human Nature,

To read

The important point is that there is no general reason for expecting genetic influences to be any more irreversible than environmental ones.

So, of the two effects that genes have on the world—manufacturing copies of themselves, and influencing phenotypes—the first is inflexible apart from the rare possibility of mutation; the second may be exceedingly flexible.

And ‘genetic variation in the population for’ a trait X is exactly what we mean when we talk, for brevity, of ‘a gene for’ X.

Unless natural selection has genetic variation to act upon, it cannot give rise to evolutionary change. It follows that where you find Darwinian adaptation there must have been genetic variation in the character concerned.

We are bound, in such discussions, to postulate, implicitly or explicitly, genes ‘for’ proposed adaptations.

Sum: How genetic determism is no bigger a concern than environmental determinism. How proclivity to do something doesn't mean they will do it. How behavior patterns require genetic variability to work in their favor.

This is simply because preventing reading would not be its most obvious or debilitating phenotypic effect.

They concluded that natural selection had favoured eggshell removal behaviour of adult gulls, because past adults who did not do it reared fewer children.

But there is no reason for them to believe that the loci controlling modern variation in an adaptation were the very same loci at which selection acted in building up the adaptation in the first place.

Just because there's a gene for something doesn't necessarily mean that it ws for this reason that the genetic variation worked

‘the removal of any of several widely spaced resistors may cause a radio set to emit howls, but it does not follow that howls are immediately associated with these resistors, or indeed that the causal relation is anything but the most indirect.

A sensible and unexceptionable way of thinking about natural selection—‘gene selectionism’—is mistaken for a strong belief about development—‘genetic determinism’.

Returning to the time-lag effect itself, since modern man has drastically changed the environment of many animals and plants over a time-scale that is negligible by ordinary evolutionary standards, we can expect to see anachronistic adaptations rather often. The hedgehog antipredator response of rolling up into a ball is sadly inadequate against motor cars.

The latter case immediately suggests a survival value for approaching light sources.

Why do moths run into flames?

That assumption was once safe.

Animals living in env diff from what selection pressures have programmed it to live in exhibit anachronistic behaviours. Which explains why moths run into flames

It is simply meaningless to speak of an absolute, context-free, phenotypic effect of a given gene.

The phenotypic effects of a gene makes sense only when the environment in which the gene exists is considered

We have now added the more subtle point that changes in the environment may change the very nature of the phenotypic character we set out to explain.

but natural selection has no foresight.

Female ants can sprout wings if they happen to be nurtured as queens, but if nurtured as workers they do not express their capacity to do so.

Does that mean if we are reared diff we would have wings?

All attempts to do this have singularly failed, apparently because the necessary genetic variation does not exist.

It need only be a quantitative brake to have dramatic qualitative effects.

If optimizing systems are concerned with maximizing something, satisficing systems get away with doing just enough.

The animal that results is not the most perfect design conceivable, nor is it merely good enough to scrape by. It is the product of a historical sequence of changes, each one of which represented, at best, the better of the alternatives that happened to be around at the time.

‘There is no such thing as a free lunch’.

Every evolutionary change comes at a cost

The evidence suggested that each wasp fought for a time proportional to her own investment, rather than proportional to the ‘true value’ of the burrow.

A popular argument for prolonging wars gave rise to the other name for the fallacy, the ‘Our boys shall not have died in vain’ fallacy.

Concorde fallacy

Is there a constraint such that the wasps’ Concordian behaviour is the best they can achieve under it?

In passing, the fundamentalist student might pause to wonder at a God who goes to great trouble to provide predators with beautiful adaptations to catch prey, while with the other hand giving prey beautiful adaptations to thwart them.

Actual contingencies will fit these general classes only approximately, and apparent mistakes are therefore bound to be made.

Sum: how we should consider that genes in the same organism will be at conflict too. How adaptation works based on the average of the conditions present. How maladaptations are rather evolutions that weren't favorable for the organism

However strongly adaptationist our beliefs may be, we can only expect animals to be average statistical optimizers, never perfect anticipators of every detail.

Firstly, it is natural to assume that even if a manipulator gets away with it temporarily, it is only a matter of evolutionary time before the lineage of manipulated organisms comes up with a counter-adaptation.

are in such a commanding position over their offspring that offspring may be forced to work in the interests of their parents’ genetic

A male cricket does not physically roll a female along the ground and into his burrow. He sits and sings, and the female comes to him under her own power. From his point of view this communication is energetically more efficient than trying to take her by force.

Signals as means of manipulation. How it might be efficient for the manipulator to use signals rather than brute force

By advancing a manipulation hypothesis we are, in effect, suggesting that the female may not be in control of her own muscles and limbs, and that the male may be.

It is lineages that evolve, and lineages that exhibit progressive trends in response to the selection pressures set up by the progressive improvements in other lineages.

Maybe the female ‘insists’ upon an exhausting performance of song by her mate before she will come into reproductive condition, thereby selecting only the most robust male for a mate.

‘This hypothetical parasitoid presumably had a life cycle that was almost synchronized with, and nearly equal in length to (but always slightly less than), the ancestral protoperiodical cicada. As the theory goes, the cicadas finally outran their parasitoid pursuer and the poor specialized beast went extinct’

How cicadas life cycle might be a result of an arms race with some extinct species

Mutations that make foxes run more slowly than rabbits might therefore survive in the fox gene-pool longer than mutations that cause rabbits to run slowly can expect to survive in the rabbit gene-pool.

The point is really one about asymmetries in strengths of selection pressure.

Finally, a fish that is very cautious about approaching worm-like objects may cut its risk of being eaten, but it also increases its risk of starving.

‘There are more worms unattached to hooks than impaled upon them; therefore, on the whole, says Nature to her fishy children, bite at every worm and take your chances’

Sum: manipulation of an organism by others. Mating manipulations by both male and female. Manipulations between parent and offspring. Asymmetry in the arms race. Life/dinner effect which means an adaptation for an organism maybe utterly necessary while some other animal might not need some adaptation that much. Fox and rabbit analogy. Rare enemy effect. Angler fish analogy

We should expect to see animals working in the interests of other animals’ genes.

Sum: Why the cost-benefit analysis can explain manipulation in nature. The cost of unsuccessful manipulation may be higher for the manipulator and the costs of getting manipulated may be lower

So much is this so that there are many records of adult passerine birds feeding a fledged young C. canorus raised by a different host species; this, like lipstick in the courtship of mankind, demonstrates successful exploitation by means of a “super-stimulus”.’

The arms race concept completes the classical supernormal stimulus explanation, by providing a functional account of the host’s maladaptive behaviour, instead of leaving it as an unexplained limitation of the nervous system.

Sum: how arms race combined with rare enemy principle can explain the maladaptive behaviors of organisms - exemplified by cuckoo parasitising other birds' nests. The stimulus provided by the parasite is termed 'super-normal stimuli'

the host workers kill their own mother and adopt the usurper.

Do not expect to see animals always behaving in such a way as to maximize their own inclusive fitness. Losers in an arms race may behave in some very odd ways indeed.

The costs of ‘bothering’ to be equipped to resist manipulation by an occasional M. santschii queen may outweigh the benefits.

Another example of super normal stimuli. Ants killing their own queen under the influence