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Saturday, November 13th, 2004


 

The Ancestor's Tale: A Pilgrimage to the Dawn of Evolution

by Richard Dawkins

A review by Doug Brown

Evolution has been a hot topic recently, due to the discovery of what appears to be a new species of Homo in Indonesia. The fossils found thus far indicate humans of surprisingly short stature, which the popular press has lost no time in dubbing "hobbits." These people seem to have been an offshoot of the Homo erectus lineage, which ran parallel to the lineage we descended from. If this turns out to be correct, then we co-existed alongside other hominid species much more recently than was previously thought. As Richard Dawkins says in The Ancestor's Tale, it's an exciting time to be a biologist; and he wrote The Ancestor's Tale before Homo floresiensis was found.

The Ancestor's Tale is a history of evolution, starting with humans and moving back through time. Along the way we rendezvous with more and more common ancestors, like streams joining together to form larger tributaries. The pilgrimage pauses for tales about some of the creatures we meet ("The Gorilla's Tale," "The Axolotl's Tale," "The Sponge's Tale," etc.), in a format loosely inspired by Chaucer's Canterbury Tales. The different tales emphasize different facets of evolution. "The Beaver's Tale" offers Dawkins a chance to discuss his extended phenotype concept, which states that the structures animals are genetically programmed to create should be considered part of the animals' phenotypes. For those who only fuzzily remember biology, genotype is the genes, and phenotype is what the organism actually looks like (genotype is the recipe, phenotype is the cake). When discussing the phenotype of a beaver, most biologists only talk about the animal's body, fur, color, etc. Dawkins suggests we should also look at the dam and the lodge, just as bird nests should be considered part of their phenotypes, and termite mounds are part and parcel of termites as organisms.

The sections at the start of the book on hominids are a good summary for folks wanting to know more about the evolutionary context of the Homo floresiensis find. I was very fortunate in just having finished that section of the book when the news broke. I'm sure Dawkins now wishes he could put out an updated edition, but even with the absence of H. floresiensis, the first several chapters provide a good overview of the tangled bush of hominid evolution.

Along the pilgrimage Dawkins clarifies several misinterpretations of his writings, revealing he is not the inflexible fervent ultra-Darwinist some have portrayed him as being. His selfish gene concept does not presuppose that genes are imbued with intentionality; he does not believe for a moment that genes want to replicate. In regards to complexity theory, while Dawkins feels natural selection is the primary evolutionary force, he allows for physics and minimum energy to also play a role in structural formation. While Dawkins and Stephen Jay Gould certainly took different views on mechanisms and processes of evolution, the popular press built it into a bitter rivalry that was largely illusory. Indeed, Gould is mentioned several times in The Ancestor's Tale as a colleague rather than an opponent, even when differences in evolutionary interpretation are emphasized.

At the end of the pilgrimage, in a chapter named "Canterbury" (continuing the Chaucer metaphor), Dawkins discusses the origin of life. Here I felt his bias towards replicators as the cornerstone of life led him into weak territory. Since his emphasis is that evolution is gene-driven, he feels genetic material is the definition of life, and life ergo started with genetic material. One major problem with this theory (sometimes called the "naked gene" theory) is that DNA and RNA are incapable of replicating themselves; a whole suite of helper proteins, enzymes, and ribosomes are required, and these require a functioning metabolism to drive their reactions. Seeing as the vast majority of organic chemical reactions are metabolic rather than replicative, it seems more probable that life began as a self-catalyzing series of metabolic reactions that later stumbled on a method of encoding themselves. Dawkins's argument that heredity came before metabolism is that metabolism is not "useful" without replication: "Without heredity, and thus natural selection, there would have been nothing to be useful for. The very idea of usefulness cannot begin until the natural selection of hereditary information does." I would reverse the argument and say genetic information is even more useless unless something already exists for it to encode; it would be absurd to argue recipes arose before cooking. Ultimately, though, usefulness is a red herring here. Nature doesn't require things to be useful in order to exist; they just have to disperse energy, which metabolic reactions do like gangbusters. Unfortunately, we will never know how life got started. Even if someone does start life in a test tube someday, we won't know for sure if that's how it started the first time around.

Despite my qualms with the "Canterbury" chapter and Dawkins's general emphasis on heredity over organismal biology, The Ancestor's Tale is still an engaging history of life on our backwater planet. There are a few British-isms throughout the text (in the UK buzzards are raptors similar to red-tailed hawks; in the US it is a slang term for vultures), but just a few. One thing that may put off some readers is that, unlike many science writers, Dawkins sees no reason to be polite to people with religious beliefs. He delights in slam-dunking creationist arguments, and lobs a few ad hominem remarks in that direction. If Thomas Huxley was nicknamed "Darwin's Bulldog" for his advocacy of Darwinian evolution, Dawkins could perhaps be called "Darwin's Rottweiler." Despite the scattered creationist jabs, The Ancestor's Tale is not a defense of evolution; Dawkins covered that ground in The Blind Watchmaker. The pilgrimage metaphor describes the book well. Like a pilgrimage, the book is not an exhaustive exploration through every corner of evolutionary history; it is a journey along one particular trajectory. As a result of that chosen course, some groups of organisms get short shrift. However, also like a pilgrimage, the journey provides enlightenment on ourselves and our place in the world.


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