About book The Extended Phenotype: The Long Reach Of The Gene (1999)
What continues to impress me about Dawkins’ writing is his accessible style, with solid opening paragraphs and good chapter endings. So much so, that I was able to trace backwards his basic ideas presented in, “The Extended Phenotype,” and translate them from the language of phenotypes to epigenetics. Phenotypes are the set of epigenetic features that change a cell. Dawkins’ openly states his thesis: “The thesis that I shall support is this. It is legitimate to speak of adaptations as being ‘for the benefit of” something, but that something is best not seen as an individual organism. It is a smaller unit, which I call the active germ line replicator. The most important kind of replicator is the gene or small genetic fragment. Replicators are not, of course, selected directly, but by proxy; they are judged by their phenotypic effects. Al though for some purposes it is convenient to think of these phenotypic effects as being packaged together in discrete vehicles such as individual organisms, this is not fundamentally necessary. Rather the replicator should be thought of as having extended phenotypic effects, consisting of all its effects on the world at large, not just its effects on the individual body in which it happens to be sitting.” p.4 Three types of extended phenotypeFirst there is a capacity of animals to alter their environment using physical constructions or creating animal artefacts, like beaver dams, termite mounds, and possibly beehive site selection and spider webs.Second, some parasitic organisms have a direct ability be alter their environment to their advantage, through the capacity to benefit from a host organism. Parasites that manipulate host behavior to facilitate its own reproduction can be found in the female Sacculina (a barnacle like parasite) that finds a male crab, penetrates its shell, sterilizes it, widens its abdomen, hormonally changes the male into a female and deposits her eggs.The third type of extended phenotype refers to an action at a distance. These are found in morphological - markers are often detectable by eye, by simple visual inspection. Many butterflies mimic the color pattern of the Monarch Butterfly, which is brought about by the nectar of milkweed. But only the Monarch is immune to the poison in milkweed and the Monarch is the only one that is poisonous if eaten by a predator. The false Monarchs indirectly benefit from the adaption of the Monarchs color pattern schemata. Or another idea is that of female choice and sexual selection and it is called indirect choice. It is the notion that females are not making active choices of males, but through their actions, they are selecting for sexually selected traits. Many courtship routines entail elaborate and vigorous chasing and the like, and a female may indirectly select the best male by performing such actions. Only the fittest male can keep up with her and she will weed out any stragglers. Selection favors the more vigorous males and any aspects of secondary sexual traits that aid in such pursuit.Daniel Dennet in the Afterword very succinctly condenses one of Dawkins major theorems that presages the present day enticing examination into epigenetics with; “Dawkins makes a very important point that a change in the environment may not just change the success rate of a phenotypic effect; it may change the phenotypic effect altogether!” I admire Dawkins not only for his clear communication style but is ability to speculate with such a reasoned capacity that his theories actually become part of everyday scientific dialogue. I also really like how Dawkins differentiates between the Gaia hypothesis and a genecentric worldview; it really helped to clear this up for me. 4.5
"[The] 'central theorem' of the extended phenotype: An animal's behaviour tends to maximize the survival of the genes 'for' that behaviour, whether or not those genes happen to be in the body of the particular animalperforming it." p233Dawkin's theory of the extended phenotype is given full expression in this his self-proclaimed favorite work. It is only now that I realize the publication of The Extended Phenotype (TEP) was in 1982, a mere three years after my favorite work of his The Selfish Gene (TSG). This close publication date explains why these two books are so similar, and why I felt like TEP was dragging its heels for the first ~200 pages.It was not until chapter 11 that Dawkins began explicating his theory, the pages spent before this point were designed to undercut the reader's focus on the individual organism as the unit of adaptive benefit and instead place his/her faith in the gene. Chapters on Arms Races and Manipulation, Active Germ-line Replicators, and Selfish DNA were slightly modified extractions from TSG and although very relevant to TEP these chapters will be redundant to anyone who is familiar with TSG. It is because of this redundancy that I can say I really liked this book, but wouldn't consider it "amazing". Apart from redundancy, TEP is a fairly accessible concept especially for anyone who's familiar with Dawkin's previous work. Genes exert a phenotypic effect, but this isn't limited to the physical body of the organism; genes also affects behavior. A beaver's dam-building behavior is equally the result of its genes as a thick coat of fur, and so it is equally valid to claim a gene 'for' fur as one 'for' dam building. There are also genes 'for' the behavior of other organisms; parasites burrow into ants (their temporary host) and modify their behavior to cause the ant to climb blades of grass and therefore becomes more susceptible to being eaten by grazing sheep (the parasite's permanent host). Here we have genes in one animal for the control of another animal. The "Bruce Effect" where male mice exude a pheromone which causes a recently inseminated female mouse to block her pregnancy shows phenotypic action at a distance. A male mouse has in his DNA a gene 'for' phenotypic effect within the DNA of a female mouse. The logical progression of this theory is awesome, and I highly recommend it to anyone interested in evolution and genetics. For those who aren't familiar with evolutionary theory there's a glossary in the back to aid reading, but even with a good foundation in evolutionary theory it was a difficult read. Like all Dawkin's books on evolution I highly recommend this.
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Four and a half. A more academic follow-up to The Selfish Gene, Dawkins' thesis here is that a set of genes (a genotype)effects a series of behaviors (a phenotype), and that that phenotype is not limited to the interior of an organism. That is, genetic effects can extend to other organisms and to the environment as well. Persuasively and ingeniously argued, this book will change your perspective on what it means to have a "genetic predisposition".Readers interested in the theories presented in The Extended Phenotye should check out the cover story to the November 2014 National Geographic magazine, "Real Zombies: The Strange Science of the Living Dead". It borrows several examples from Dawkins' sources and research, and re-validates his theory for 21st century research.
—Sarah
Richard Dawkins here explains his view that the largest unit on which natural selection can reasonably be said to operate is the gene rather than the organism, and explores this idea’s consequences for the standard conceptions of organisms, groups, and selection. The motif he introduces to show this best is a Necker Cube, which is a simple line drawing of all the edges of a cube: when looked at for the first time, it seems to be an overhead view of the cube. But with some visual effort, you can make your brain interpret the exact same stimulus as a view from below. Your two perspectives can be shifted between without many problems at all. This an slightly off analogy, because the two views of the cube have no reason to prefer one over the other, whereas Dawkins clearly believes that his focus on the gene is more proper than some biologists’ focus on the organism. Another analogy: we often hear from nature documentaries and wide-eyed wonderers how harmonious the biological systems of Earth are: how fortunate that some things breathe carbon dioxide and some breathe oxygen, that both cheetah and gazelle are lithe and fast in their dance of predation, that symbiotic pairs of species fill each other’s needs so well. But this is an illusion: the different organisms of the planet do not evolve their interplay from any interest in harmony on the part of nature. Rather, given that every other organism already exists, a certain organism will have its various genotypes selected for or against depending on how their expressed phenotypes allow them to be ruthless exploiters and reproducers. Similarly, the genes that make up a genotype are not selected for their harmonious interaction. Instead, at each locus, the alleles that are best able to propagate themselves via their modifications of the expressed phenotype, given their fellow genes, will be selected for. The key difference is that the balance is not driven by a push towards harmony but the ruthless interactions and pushes for self-replication between a myriad of different genes.Dawkins pushes this concept far in this book: he explores parasitism, evolutionary arms races, sex ratios, and embryology with an expert’s touch. But by far the most gripping part comes from his title: the extended phenotype is what happens when a gene’s reach extends beyond the physical boundaries of its host organism. A gene can influence the structure of the containing organism, and this surely is a phenotype, but Dawkins gradually pushes this further: a baby bird’s gene influences its parent to feed it, a beaver’s gene pushes it to build a larger dam, and a songbird’s gene summons another bird to come and mate, transferring the risk of travel to that other creature. The most difficult to grasp concept in this book, but in my mind the most fruitful, is the idea that an organism’s behavior tends to increase the success of the gene responsible for that behavior, no matter whether that gene resides in that organism (or indeed even in the same species) or not. While this is a book starting its fourth decade, it still feels very fresh and eye-opening. A word of warning: the book is more technical than various popular books from Dawkins; if you feel like you could tackle a college-level evolutionary biology class you can handle this, though.
—Bob Anderson
This is the follow up to Richard Dawkins' first book The Selfish Gene. It is aimed at people who have some formal training in biology, specifically biology undergraduate students. It is also packed with much more jargon than any of his other books, consequently it does require more effort on part of the layman reader.But all effort required to properly understand The Extended Phenotype is well worth it. It pays off immensely. Suffice it to say, that the central concept of the book The Long Reach of the Gene, left me in awe once I grasped its meaning and implications. It is such a wondrous way to look at evolution, and I can safely say that, probably, such a great insight would have eluded me entirely, regardless of how much I like to think about such things.Therefore I would like to thank Richard Dawkins for bringing such marvels of nature to my, and the public's attention.
—Loránd Szakács
