دانلود کتاب Life's Origin: The Beginnings of Biological Evolution

In a word: disappointed. I came to this book expecting to see more of the excellent work displayed in Dr. Schopf's previous book, Cradle of Life: The Discovery of Earth's Earliest Fossils (1999). Instead I found a rehashing of some of the standard, and in my view time-worn theories about the origin of life -- all of which end up rather indefinite, speculative and unsatisfying.

Some of the stuff isn't even accurate: it is not true that "Miller's experiment showed for the first time that amino acids can be produced under simulated 'primitive Earth conditions'." (p18) Never mind the fact that Miller's simulated conditions are a far cry from primitive conditions (see the discussion, pp67-68). Miller wasn't even the first to do these experiments: See Yockey, Information Theory, Evolution, and The Origin of Life, page 125ff; Miller's was a repeat of "experiments of Walther Löb et al in 1922."

Incidentally, I would think that the composition of the early earth environment would naturally come from a study of planet formation by accretion - a natural topic of astrophysics. I think the answer is: NOT an ammonia/methane environment!! for reasons that have to do with the chemistry that results from the cooling of a molten inner planet. One of my favorite books on this subject is Peter D. Ward and Donald Brownlee, Rare Earth: Why Complex Life is Uncommon in the Universe. See also Christopher Wills and Jeffrey Bada, The Spark Of Life: Darwin And The Primeval Soup and Wallace S. Broecker, How to Build a Habitable Planet.

I assume that this book is a compilation of papers that he uses in his college courses. Nothing wrong with that, but I had anticipated something much better. I have great respect for his work in Cradle of Life, and his participation in the 1998 NRC Symposium, Size Limits of Very Small Microorganisms: Proceedings of a Workshop (Compass Series (Washington, D.C.).). I had hoped for some further insights that follow on from the implications of that symposium, in particular.

The most interesting chapter concerns the "Tree of Life" written by Dr. Schopf himself. Genetic research has constructed its own tree based on the recurrence of similar gene packages. Widely different animal species share the same "hox" gene packages for appendages (legs, antennae, etc.), eyes, etc. Some packages appear to have been in place and largely unchanged since (at least) the Cambrian Era, some 500 million years ago. Barely noted in his book is the ultimate "package" that is essentially the same for all plants and animals: the so-called "central dogma" that determines the genetic coding in the DNA, and the elaborate process by which this is transformed into the useful life chemicals.

If one insists on evolution by purely natural processes, this recurrence of similar gene packages is a powerful "proof" that these diverse species share a common ancestor, and in particular that all of life evolved from an original first living cell "[s]ince any complete biochemical system is far too elaborate to have evolved more than once in the history of life...." (p.163). This is of course no explanation of how the packages came to be in the first place -- and the book's probes into this issue (which is after all the subject of the entire book) come to singularly weak and unconvincing conclusions.

There will always, I think, be a chasm between Creationists and Naturalists, regarding life's origins. The Creationist sees natural descent as a possible but not necessary conclusion of the genetic tree of life: similar gene packages may just show that the Creator re-used them. Proof of a natural process is not just asserting "it must be so" but in showing such relatedness in the laboratory or in mathematical simulation based on demonstrable assumptions about physical or chemical processes. Otherwise, the claim is metaphysics or religion, but certainly not science.

In my view, the theory of evolution has made great advances exactly in proportion to the effort it has given to such experimentation. I love to discover (with the help of great authors) new things about the power of natural processes through laboratory experimentation, for example in Sean B. Carroll's Endless Forms Most Beautiful: The New Science of Evo Devo - a book that I recommend highly. I would similarly look forward to a demonstration of relatedness by simulation (at one time I conjectured that evolution of the trilobite phacops eye can be explained by simulation on the basis of a combination of arrested development and environmental pressure).

I look forward to another book by Schopf that will similarly expand my understanding of Life's Origins -- but without the tired "just so" stories found in this book.

HMSChallenger