THE notion of the “selfish gene” is the most successful scientific metaphor of the past 30 years, followed not far behind by “the extended phenotype”. Both were coined by Richard Dawkins and are, as it happens, the titles of his first popular science books.
The Selfish Gene‘s message was that evolution is about the natural selection of genes, and genes alone. Dawkins sees them as the best candidates to be evolution’s units of replication. As such, the genes that are passed on are those whose consequences serve their own interests at gene level – that is, to continue being replicated – and do not necessarily serve the interests of the organism at a larger level, or at the level of groups of organisms. It is “as if” these genes are being selfish, not that they are really selfish.
The Extended Phenotype develops this idea, arguing that in their drive for survival and replication, genes extend their influence beyond the appearance, or phenotype, of an individual and into the world where it also affects their chance of survival. Think of the beaver’s dam or spider’s web.
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For reasons to do with how science is communicated, a human love of simple narratives, and Dawkins’s energetic advocacy of these metaphors, the public has been left with a view of evolution and Darwinism which does not truly reflect thinking among evolutionary biologists. This view also perpetuates the existence of “opposing camps” when there is no need. Worse, it skews popular notions of Darwinism. This is why these metaphors are so important: metaphors stretch to the heart of “what science is for” and to the kind of answers it can provide.
Take heredity. If you only read Dawkins, you might think that the case has long been closed on how it works. In fact, there are competing perspectives stretching back over 150 years. Darwin himself was a pluralist and proposed a theory of heredity that allowed not only for the inheritance of latent characteristics but also for the environment to play a role in it. According to Darwin and many who followed, the environment could even have an impact on the germ cells: in other words, the gene line is not necessarily “immortal”.
Research reflecting this plurality survived outside the mainstream throughout the 20th century. Today, building on the legacy of work by researchers such as Conrad Waddington or Barbara McClintock, increasing numbers of biologists find it hard to doubt the environment has a powerful impact on gene expression during an organism’s lifetime.
The public’s largely Dawkinsian view will be further challenged by research now emerging that may point to this kind of environmental influence being passed on to offspring epigenetically. Researchers have known for some time about transgenerational epigenetic effects in plants and fungi, and it is becoming clear that they might occur in animals too.
Another area of research that could challenge Dawkins’s metaphors is lateral gene transfer (LGT), which describes how an organism incorporates genetic material from another organism without being its offspring, as opposed to vertical transfer, in which genetic material is transmitted from parent to offspring.
Most of us know about LGT through antibiotic resistance, where one bacterium transfers genetic information to another that gives it immunity to a type of antibiotics. At first it seemed as if LGT affected only single-celled microbes, which reproduce asexually, but there is increasing evidence that it also occurs in animals and plants.
LGT may not completely bring down the neatly branching tree of life as Darwin envisaged it, but at the very least it raises questions about what is happening at the roots. Some see LGT as a challenge to Dawkins’s idea of a linear, immortal, insulated gene line. However, it is important to note that LGT does not necessarily challenge Dawkins’s selfish gene metaphor: these transposable elements could be seen as a sort of selfish replicator as outlined in The Extended Phenotype. After all, LGT is just another way for such genes to replicate themselves, and genes only have to have the potential to be immortal to fit Dawkins’s definition of “selfish”. What is clear is that as our picture of relationships between species, and between genes and their environment, becomes increasingly fluid, Dawkins’s metaphors are shown to reveal only a small part of a much bigger picture.
Scientific metaphor should be about the best interpretation of evidence and about opening up new research vistas. The selfish gene metaphor claims that only genes or replicators are inherited and are essentially immortal, and it offers an interpretation of evolutionary biology in that light.
We are testing that empirical claim and finding that things are a lot more complicated and subtle. This must mean that as an organising interpretation of evolutionary biology, the metaphor of the selfish gene and, by extension, that of the extended phenotype, are insufficient. They are now problematic because what they claim or offer is no longer as good as the alternative analyses.
While Dawkins’s contribution is indisputable, his strong advocacy of a narrow-focus view of evolution is rightly being called into question. It paints an inflexible picture not only of the evolutionary sciences, but also of how science works. This in turn closes off dialogue in both public and academic spheres. It can, at worst, constrain future research. Nowhere is this more evident than in theories about environmentally driven acquired characters, which have long had a reputation as Darwinian “heresy”.
“Dawkins’s contribution is indisputable, but his narrow view of evolution is being called into question”
We must think about moving on from communicating evolutionary science with the kind of rhetoric and sweeping advocacy Dawkins’s metaphors have encouraged towards a more nuanced exploration of the complexity involved.
