The Greatest Show on Earth: The Evidence for Evolution

Background

Synopsis

• "Only a theory?" examines evolution as theory and fact. He cites the Oxford English Dictionary's definition of "theory": “A scheme or system of ideas or statements held as an explanation or account of a group of facts or phenomena; a hypothesis that has been confirmed or established by observation or experiment, and is propounded or accepted as accounting for the known facts; a statement of what are held to be the general laws, principles, or causes of something known or observed.”
• "Dogs, cows and cabbages" examines artificial selection, which Dawkins calls "sculpting the gene pool." He notes that from wild cabbage, breeders have made "broccoli, cauliflower, kohlrabi, kale, Brussels sprouts, spring greens, romanescu and, of course, the various kinds of vegetables that are still commonly called cabbage.... Another familiar example is the sculpting of the wolf, Canis lupus, into the two hundred or so breeds of dog, Canis familiaris, that are recognized as separate by the UK Kennel Club.”
• "The primrose path to macro-evolution" examines coevolution. Flowers produce nectar to lure pollinators. Bees select for floral beauty, albeit unconsciously. Beauty is in the eye of the beholder. Oenothera has evolved patterns invisible to us but not to bees, who see in ultraviolet light. There is an orchid, Angraecum sesquipedale, with a sixteen-inch nectary. Darwin and Alfred Russel Wallace, who codiscovered the engine of evolution, made a prediction: there must be a moth with a proboscis long enough to pollinate it. Such a moth, Xanthopan, was discovered. Orchids like Drakaea have evolved to mimic female insects. He revisits artificial selection, describing Cyril G. Hopkins's Illinois long-term selection experiment and Dmitry Belyaev’s work on the domesticated silver fox. He introduces sexual selection, “selective breeding by females of males.” This leads to natural selection, in which “nature is the selecting agent.”
• "Silence and slow time" examines the age of the Earth and geologic time. Dawkins describes various means of dating the earth, notably dendrochronology and uranium-lead dating.
• "Before our very eyes" examines examples of evolution in the field and in the lab. In 1971, a population of Podarcis sicula from the island of Pod Kopiste was transported to the island of Pod Mrcaru. In 2008, a group of scientists led by Anthony Herrel found that the lizards had evolved stronger jaws to adapt to a vegetarian diet, and have started to evolve a cecum. Dawkins describes Richard Lenski's E. coli long-term evolution experiment, in which 12 strains of E. coli were grown in flasks with glucose as a limiting factor. “In these conditions, the Darwinian expectation was that, if any mutation arose that assisted an individual bacterium to exploit glucose more efficiently, natural selection would favour it, and it would spread throughout through the flask as mutant individuals out-reproduced non-mutant individuals.” That is what happened: “As the ‘flask generations’ went by, all twelve lines improved over their ancestors: got better at exploiting glucose as a food source. But, fascinatingly, they got better in different ways – that is, different tribes developed different sets of mutations.” Lenski's student Zachary Blount found that one strain evolved the ability to digest citrate. A tragic corollary is antimicrobial resistance; bacteria have evolved resistance "to antibiotics in spectacularly short periods. After all, the first antibiotic, penicillin, was developed, heroically, by Florey and Chain as recently as the Second World War. New antibiotics have been coming out at frequent intervals since then, and bacteria have evolved resistance to just about every one of them.” He describes John Endler’s studies of the competing pressures of natural and sexual selection. Endler found that in streams without strong predation, male guppies evolved colorful spots to attract females. In streams with strong predation, they evolved camouflage to escape detection. Endler wanted to see if he could recreate this in the lab. He raised guppies in ponds with strong, weak and intermediate predation. After introducing a strong predator, the number of spots plummeted. The sizes of rocks in the ponds also influenced the sizes of spots the guppies evolved.
• "Missing link? What do you mean, 'missing'?" examines paleontology. J. B. S. Haldane was asked for an observation that would disprove evolution. He replied, “Fossil rabbits in the Precambrian!” No such anachronistic fossils have been found. Several transitional fossils have been found, starting with Archaeopteryx, an early bird. He traces transitional fossils in tetrapod evolution: Eusthenopteron and Ichthyostega had characteristics of both fish and amphibians. There was a gap between Panderichthys and Acanthostega; it was filled by Neil Shubin and Ted Daeschler's discovery of Tiktaalik roseae. He looks at the evolution of whales, documented by Pakicetus, Basilosaurus, Rodhocetus and Ambulocetus. He discusses Puijila darwini, a primitive pinniped discovered as the book was heading to press.
• "Missing persons? Missing no longer" examines transitional fossils in human evolution, notably Pithecanthropus erectus and Australopithecus afarensis.
• "You did it yourself in nine months" discusses developmental biology, especially the work of Lewis Wolpert. Haldane was asked how, in evolution, a single cell could give rise to something as complex as a human. His response is the chapter title.
• "The ark of the continents" examines biogeography. Darwin's observations on the HMS Beagle led to his theory. Species are found in specific places; lemurs in Madagascar; platyrrhine monkeys in South America; catarrhine monkeys in Africa and Asia. New Zealand has no endemic species of mammals, besides bats Gaps in Darwin's knowledge have been filled by Alfred Wegener's discovery of plate tectonics. Geographic isolation drives speciation, as a young Darwin intuited.
• "The tree of cousinship" examines the tree of life. Dawkins discusses homology. He discusses Motoo Kimura's neutral theory of molecular evolution. Silent mutations are invisible to natural selection but not to biologists, who use them as molecular clocks to see when species split. Dawkins discusses pseudogenes, vestiges of functional genes: "The very existence of pseudogenes - useless, untranscribed genes that bear a marked resemblance to useful genes - is a perfect example of the way animals and plants have their history written all over them."
• "History written all over us" examines vestigiality and unintelligent design
• "Arms races and 'evolutionary theodicy'" examines evolutionary arms races between predator and prey and host and parasite. “Over evolutionary time, predators get better at catching prey, which prompts prey animals to get better at evading capture.” He examines cruelty in nature, such as Ichneumonidae, wasps that lay their larva in live caterpillars, which they consume from the inside out. Dawkins argues that such things do not reflect a loving creator, but rather evolution by natural selection.
• "There is grandeur in this view of life" is a close reading of the final passage of On the Origin of Species. He writes that understanding evolution ennobles us: "We are surrounded by endless forms, most beautiful and most wonderful, and it is no accident, but the direct consequence of evolution by non-random selection, the only game in town, the greatest show on earth."

Critical reception