The Extended Phenotype by Richard Dawkins
The Extended Phenotype by Richard Dawkins

Science · 1982

The Extended Phenotype review

by Richard Dawkins

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The verdict

The Extended Phenotype is Richard Dawkins's most technical and, by his own account, most important book.

Best for readers comfortable with technical depth. Reading time: 7h 15m.

The Extended Phenotype by Richard Dawkins
The Extended Phenotype by Richard Dawkins

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What it argues

The Extended Phenotype is Richard Dawkins's most technical and, by his own account, most important book. Where The Selfish Gene popularized the gene's-eye view of evolution for general audiences, The Extended Phenotype works out the logical implications of that view more carefully and argues for the concept that gives the book its title: the idea that a gene's phenotype — its effects on the world — need not be limited to the body it inhabits. Genes can have effects that reach beyond the organism into the environment, and natural selection acts on those extended effects just as it acts on anatomical features.

The central examples of extended phenotypes are striking. A caddisfly larva builds a case of stones and pebbles around itself; genetic variation among larvae produces measurable variation in the cases. Selection acts on the cases as surely as it acts on the bodies inside them. Beavers build dams; the dam is an expression of the beaver's genes in the world. Parasites manipulate host behavior — a fluke that causes snails to grow thicker shells, a wasp that parasitizes a caterpillar and causes it to stand guard over the wasp's cocoon. In all these cases, a gene influences the world beyond the boundary of its host organism's skin.

What it gets right

  1. 1.

    A gene's phenotype — its effects that natural selection can act on — is not limited to the organism that contains it. Genes can influence the world through artifacts, other organisms, and behavioral manipulation.

  2. 2.

    The extended phenotype concept includes cases like beaver dams, caddisfly cases, and parasite-manipulated host behavior, where genetic variation produces variation in structures or behaviors outside the organism's body.

  3. 3.

    Parasites that manipulate host behavior illustrate how genes from one organism can effectively control the phenotype of another, blurring the functional boundary between organisms.

What it covers

Who wrote it

Richard Dawkins is a British evolutionary biologist and emeritus professor at Oxford University. He held the Charles Simonyi Chair for the Public Understanding of Science from 1995 to 2008. His books include The Selfish Gene, The Blind Watchmaker, The Ancestor's Tale, and The God Delusion. The Extended Phenotype, published in 1982, is his only book addressed primarily to a professional scientific audience. Dawkins considers it his most significant scientific contribution. He lives in Oxford and writes regularly on evolution and atheism.

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