Richard Dawkins: spiderwebs are Extended Phenotypes

Richard Dawkins, 1989
The Extended Phenotype
The long Reach of the Gene

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. 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):

1. the spider's web is an adaptation resulting from natural selection  
2. natural selection only acts on genes
3. 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

1. My previous blog was about spider webs: Forbidden colours: backlight spiderwebs (part 2) and more surprising finds.  
2. "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!

 

Previous blogs

• Five objections to the selfish gene theory, 26 Jan 2026 
• Spiderweb colors violate the rainbow rule 29 July 2026

 

 

Further Reading 

• Evolutionary Phenomics (youtube) with biologist Anjali Goswami.
• Phenomics: the next challenge. (2010). Review article.
• Richard Dawkins - Philosophy of Extended Evolutionary Synthesis  youtube 11:22 min. ("there must be genes for...") Typically, he doesn't investigate Niche Construction seriously and discards it.