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CHAPTER THIRTEEN CHAPTER FOURTEEN SteveJones is professor of genetics at University College London Recapitulation and Conclusion In which Darwin expounds his 10ng argument" and addresses the "mystery of mysteries": wf]y there are 50 many different species Acentury and ahalf after The Origin, Darwin can be seen to have been triumphantly right about almost everything. Evoiution Is now no more "just a theory" than is chemistry and,like all other sciences, it provides a logical wayoflooking at the worid. As he dared only to hope in that great book, light has been cast upon not lust the worlds of plants and animals, but on ourselves and our origins. Darwinism makes sense ofwhatwas once no more than a jwnble of unconnected facts, and in so doing unifies biology. Modem psychology, ecology and more find their birthplace in the pages of his greatestwork. Acentwy-and-a-halfon, evolution is as central to our understanding ofllfe as gravity Is to the study of the universe. The closing words of The Origin say it all: ''There is grandeur in thisview of life, withits several powers, having been originallybreathed into afewfonns or into one; and that. whilst thisplanethasgone cycling on according to the fixed law of gravity; from so slmplea beghmlng endless fonns most beautiful and most wonderful have been, and are being, evolved." • Mutual Affinities of Organic Beings: Morphology: Embryology: Rudimentary Organs In which Darwin considers classification andshows how his theory can be used to organise the living world along evolutionary lines As the past is the key to the present, so Is the revealwholekingdoms of existence qulte infant the key to the aduit. Darwin realised unknown onlya few decades ago. that animals adopt the fonn which is adapted The new tree of life is a direct descendant of to their own evolvedway of life as they develop. the singie sketch of shared descent that appears As a result, the deep relatedness between in The Origin. It is based on comparing the organisms might more readily be seen by billions of DNA sequences now available from comparing embryonicforms. across the whole of existence.The affInityof Darwin spent eight years working on whales with giraffes Is a mlnor surprise when barnacles, then an entirely obscure group but compared with discovery of the relatively close known to be related to crabs, insects and. other affinity of all animals to mushrooms, and the jointed-limbed creatures. Adult barnacles vary emergence ofa whole new kingdom of single- in form from the familiar seashore kind to a celled creatures, the Arch.... whichhavea sinisterversion that is an internal parasite of structure and. awayoflife entirelydifferent from crabs and resembles a giant fungus. Whatever the bacteria that they superftclally resembie. the divergence among the adults, though, the They may evenhave with them,ln embryos are remarkablysimilar.Theyalso the earlydays of life, to provide the nudeated resemble, to alesser extent, the embryos of cells that build all plants and animals oftoday. lobsters and crabs, and other jointed-legged creatures of the seas. All those in tum show affinities to the embryos of insects, a hint that butterflies haverelatives on wave-battered shores, while that great group is in turn united in its earliest development with tapewonns and their relatives - creatures entirely different in their adult fonn. This shared identity, lost as the animals grow, shows how the embryo can reveal deep patterns of descent with modification, hidden as developmentgoes on. Darwin's own classification of life -of groups within groups as evidence ofa shared hierarchy of descent that encompasses not just bamaeles and butterllies but birds and bananas-turned only on what he couldsee with the nakedeye, or down the microscope. Now genes-theunitsof evolution - have come to the rescue, and they How did a bird that cannot fly get scattered across thesouthem hemisphere? I' I 14 November 20091 NewScientist 1 Page seven
