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''River Out of Eden: A Darwinian View of Life'' is a 1995 popular science book by Richard Dawkins. The book is about Darwinian evolution and includes summaries of the topics covered in his earlier books, ''The Selfish Gene'', ''The Extended Phenotype'' and ''The Blind Watchmaker''. It is part of the ''Science Masters'' series and is Dawkins's shortest book. It also includes illustrations by Lalla Ward, Dawkins's wife. The book's name is derived from passage 2:10 of Genesis relating to the Garden of Eden. The King James Version reads "And a river went out of Eden to water the garden; and from thence it was parted, and became into four heads." ''River Out of Eden'' comprises five chapters. The first chapter lays down the framework on which the rest of the book is built, that life is a river of genes flowing through geological time where organisms are mere temporary bodies. The second chapter shows how human ancestry can be traced via many gene pathways to different ''most recent common ancestors'', with special emphasis on the ''African Eve''. The third chapter describes how gradual enhancement via natural selection is the only mechanism which can create the complexity we observe all around us in nature. The fourth chapter expounds on the utter indifference of genes towards organisms they build and discard, in their relentless drive to maximise their own utility functions. The last chapter summarises milestones during the evolution of life on Earth and speculates on how similar processes may work in alien planetary systems. == The digital river == Dawkins begins the book with a startling, yet true, claim on behalf of all organisms that have ever lived: not a single one of our ancestors died before they reached adulthood and begot at least one child. In a world where most organisms die before they can procreate, descendants are common but ancestors are rare. But we can all claim an unbroken chain of successful ancestors all the way back to the first single-celled organism. If the ''success'' of an organism is measured by its ability to survive and reproduce, then all living organisms can be said to have inherited ''good genes'' from ''successful ancestors'' instead of less successful contemporaries. Each generation of organisms is a sieve against which replicated and mutated genes are tested. Good genes fall through the sieve into the next generation while bad genes are weeded out. This explains why organisms become better and better at whatever it takes to ''succeed'', and is in stark contrast to Lamarckism. Successful organisms do not and cannot refine their genes during their lifetime. Rather, good genes make successful organisms which perpetuate good genes themselves. Following this gene-centered view of evolution, it can be argued that an organism is no more than a temporary body in which a set of companion genes (actually alleles) co-operate toward a common goal: to grow the organism into adulthood, before they part company and go on their separate ways in bodies of the organism's progenies. Temporary bodies are created and discarded, but good genes live forever in the form of perfect replicas of themselves, a result of high-fidelity copy process which is typical of digital encoding. Through meiosis (sexual reproduction), immortal genes find themselves sharing temporary bodies with different set of intimate companion genes in successive generations of organisms. Thus genes can be said to flow in a river through geological time. Scoop up a bucket of genes from the river of genes, and we have an organism. Even though genes are selfish, over the long run every gene needs to be compatible with all other genes in the gene pool of a population of organisms, to produce successful organisms. A river of genes may fork into two branches, mostly due to the geographical separation between two populations of organisms. Because genes in the two branches never share the same bodies, they may drift apart until genes from the two branches become incompatible. Organism created by these two branches (or two rivers) will form separate, non-interbreeding species, completing the process of speciation.〔( "Revolutionary Evolutionist" ), profile by Michael Schrage, ''Wired'', July 1995.〕〔("Darwin's dangerous disciple" ), interview with Frank Miele, ''Scepsis'', 1995.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「River Out of Eden」の詳細全文を読む スポンサード リンク
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