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Richard Dawkins, 1989
The Extended Phenotype
The long Reach of the Gene
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Richard Dawkins uses the spider web [1] as an example of an extended
phenotype, in his book in The Extended Phenotype. The definition of 'phenotype' is all observable traits of an organism,
in contrast to the genotype, which is -in short- DNA. The main argument of
this book is that constructs like spiderwebs, although not part of the
body, but produced by an animal, belong to the phenotype. So, the spiderweb is viewed as an extension of the body of the
spider. Hence: the spiderweb is an extended phenotype.
Dawkins writes: "In a very real sense her web is a temporary functional
extension of her body". Does his new interest in bodies and phenotypes
mean a shift from gene-centrism to organism-centrism? Not at
all! Dawkins did not quietly abandon his gene-centric view. He
argues that an extended phenotype includes all the effects that a
gene has on its environment. So, in his view genes are still in charge [3]. We are back to the The Selfish Gene:
"We are survival machines – robot vehicles blindly programmed to
preserve the selfish molecules known as genes."
Ultimately genes control the architecture of the spider's web in
an yet unknown way [2]. Contrary what the title The Extended Phenotype suggest, this book is not an organism-centered view of life. It is
still gene-centered.
As explained in his famous book The Selfish Gene, natural
selection (ultimately) acts on genes. Bodies are throw-away
vehicles of genes. Bodies die and decompose, but genes are
transmitted to the next generation. So genes are the entities that
matter in evolution. That's why Dawkins claims that natural selection acts
on genes. It makes sense that from an evolutionary perspective
genes are more important than bodies. So, if you think about it,
it's surprising that Dawkins devote a whole book on phenotypes! Why waste
a book on throw-away bodies? Could it be that bodies are important after
all? Don't worry, genes continue to control everything. The
subtitle of the book is an unmistakable reminder : "The Long Reach of the
Gene"! In order not be misunderstood, he added it in the title of
his book. The phenotype is subordinated to the genotype; the
genotype remains the most important.
But now it gets really interesting:
"Once again, I know of no genetic analysis of spider web morphology, but
there is nothing difficult in principe about imaging such an
analysis. (...) Indeed, our belief that spiders' webs have evolved
their efficient shape through natural selection necessarily
commits us to a belief that, at least in the past, web
variation must have been under genetic influence. (...) By
whatever embryological routes the genes may work in detail, the small
extra step from behaviour to web is not any more difficult to
conceive of than the many causal steps which preceded the
behavioural effect." (page 198–199 Oxford paperback 1989 edition). (my emphasis).
What strikes me are the words "commits us to a belief ". How could that be science?
Also, his lack of interest in the evidence for the genetics of spiderwebs is
surprising [2]. A scientist cannot replace lab research with imagination
or assumptions. It has to do with his commitment. Once committed to (1)
and (2):
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the spider's web is an adaptation resulting from natural
selection
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natural selection only acts on genes
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so spider's webs are determined by genes
Statement-3 logically follows from statement-1 and
statement-2. It is becoming a necessity. If we can't find a genetic cause, this does
not invalidate statement-3! We simply have to search harder! But why would
we invest money to find out precisely how genes influence the
spider's web? This is not interesting anymore. It is a theoretical
necessity. But then Dawkins is committed to a belief that is not in need to be
tested. I don't say his belief is false. It is not an unreasonble belief. It may
turn out to be true. The point is that a belief is not the same as a testable and falsifiable
hypothesis.
Are (1) and (2) necessities too? Is the spider's web necessarily an
adaptation? Has the spider's web necessarily been created by mutation and natural selection? Where
is the evidence? If no evidence is required, then the core of the theory
of evolution is a logical necessity! Then Evolution is necessarily true! I
am very, very worried about this situation. It scares me. Scientific theories must always remain tentative because new evidence can
always challenge or modify the theory. Scientific theories must always be verifiable and falsifiable. And they
must be actually tested in practice. Making the theory of evolution a necessity is to elevate it to a
scientific law similar to the
Second Law of Thermodynamics. If some experimental results contradict the Second Law, physicists will
conclude that the experiment was flawed. Has the theory of evolution really risen to the level of the invulnerable and unshakeable Second Law?
In other words: if an experiment contradicts The Theory of Evolution, the
experiment is necessarily flawed?
Oh my dear God! What have I done? I started with Dawkins' relatively
innocent claim that spiderwebs are Extended Phenotypes, and ended with the
philosophical question whether the theory of evolution has the same status
as The Second Law of Thermodynamics!
Alternatively, we could conclude that Richard Dawkins with his beliefs,
comittments and gene-centrism is just not a good scientist.
Notes
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My previous blog was about spider webs:
Forbidden colours: backlight spiderwebs (part 2) and more surprising
finds.
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"One female
Zygiella-x-notata, for instance, was seen to build more than 100 webs, all lacking a
particular concentric ring" (page 199). Please note that there is no
evidence that is genetically determined!
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The logic of the argument can be formalized as follows:
- 1. Phenotypes
are fully or partly genetically determined
- 2 Extended phenotypes are
phenotypes
- 3. Conclusion: extended penotypes are fully or partly
genetically determined.
In this way Dawkins has subsumed extended phenotypes in his gene-centric view of evolution. 6 Sep 2026
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