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Her new book, Acquiring Genomes: A Theory of the Origins of Species, extends and deepens that argument. Margulis sets out to prove that new species rarely if ever appear as the result of mutation, isolation, genetic drift, or population bottlenecks--the meat and potatoes of neo-Darwinism. Instead she maintains that the major engine of evolutionary change, the source of most of the new forms that natural selection edits, is symbiogenesis--the acquisition of whole genomes as the result of symbiotic associations between different kinds of organisms. (Knowing that some people will seize on her thesis as an attack on the theory of evolution as a whole, Margulis makes it clear that she fully supports Darwin's great discovery of the mechanism of natural selection. She simply thinks that neo-Darwinists have failed to recognize the enormous creative power of genomic mergers.)
Readers who are familiar with Margulis' earlier works will recognize her vivid, personal and sometimes impressionistic writing style. I found this book, co-authored by her son, Dorion Sagan, to be clear and accessible. Starting with Chapter 9, where Margulis presents her latest ideas on the symbiotic origin of the nucleus itself, things get a bit more technical. Margulis makes every effort to help readers through the thicket of important, but at times tongue-twisting terms, and supplements explanations in the text with an excellent glossary. Margulis also presents the findings of several other researchers whose work supports or relates closely to her own.
Readers may or may not close the book convinced that Margulis is right and the neo-Darwinists are wrong. But they will come away with a vastly deeper understanding of the pervasive nature and power of the microbial world, and of symbiosis. Margulis reveals a hidden side of nature, in which microbes have generated most if not all of life's metabolic machinery, in which vastly different life-forms consort in a myriad of ways, and in which the acquisition of entire genomes provides the raw material for great evolutionary leaps. Anyone with a deep interest in biology will gain important insights from "Acquiring Genomes."
Robert Adler, author of Science Firsts: From the Creation of Science to the Science of Creation (Wiley & Sons, 2002).
This is one of those groundbreaking books that trys to answer one of Charles Darwin's long standing mysteries... how do species originate. Darwin could never quit put his finger on the answer, he was close and I'm sure with time and the right equipment, like what is available today, he might have even solved this nagging question.
Margulis has been working on this same question for the last thirty years and she makes a very convincing argument, symbiotic merger is the main thrust of her thesis in this book. This book has some real mind-spinning ideas and you'll have to know some biochemistry, biology, chemistry, cell-biology to prepare yourself for a provocative wild ride through this book as some of the material directly challenges the assumptions that we hold about diversity in the living world.
Margulis has for many years been the leader in the interpretation of evolutionary entities as the products of symbiogenesis. Symbiogenesis is the major theme of this book. The authors show convinvingly that an unexpectedly large proportion of the evolutionary lineages had their origins in symbiogenesis. Ok, I know some of you are saying what is symbiogenesis, well it's the combination of two totally different genomes form a symbiotic consortium which becomes the target of selection as a single entity. This is achieved by the mutual stability of the relationship, symbiosis differs from other cases of interaction such as carnivory, herbivory, and parasitism.
Now, that I've said all of that, you realize that this book can get pretty deep at times, but the author has a pleasent styled narrative, always keeping the reader involved. Prehaps the greatest merit of this book is that it introduces the reader to the fascinating world of microbes, delving into providing an enthralling description of protists and bacteria.
I found this book to be most enlightening about the enigma of evolutionary biology and how species are formed, comprehensive in scope and supported by scientific theory. This book will make you think. If you want to know about the cutting edge of evolutionary thinking then this is the book for you. To realize that everything on earth is inter-related and that life will carry on when faced with tragedy.
Prof. Margulis' book also assumes a reader with a broad scientific background , largely in areas considered "old fashioned" in the 21st century. She demands an upper college level familiarity with invertebrate biology, physiology, microbiology, ultrastructure, biophysical chemistry, metabolic pathways and *GASP* thermodynamics. Then she integrates molecular biology and genomics, as needed, into the picture, to make a very convincing case for symbiogenesis. She also evokes wrath for bringing up the name of Jean Baptiste Lamarck, which is sure to raise a red flag in neodarwinist circles. Last, she does not refute the contribution of neodarwinists, she simply tries to put them in perspective.
The founding premise is that mutations constantly occur during the natural history of a species. Many experiments suggest 99% of these mutations are either silent or deleterious. Therefore, they probably cannot be counted on to drive evolution to improve on a species, let alone create new ones. Instead, a more likely pathway is for two species, with one bacterial, one eucaryotic, to coexist if it causes them to have a survival advantage when they do so. If it is in both organisms' best interest, this coexistance becomes more intimate, and can lead to the eucaryotic organism taking the smaller genome into its chromosome and making one very new and improved species. This, and many intermediate stages, are seen among invertebrates, such as Geosiphon pyriforme, a hybrid organism with a fungal (Endogone) and a cyanobacter (Nostoc) ancestor. The Geosiphon has retained the ability to fix carbon dioxide and nitrogen, receiving one multigene trait from one ancestor and the other from the partner species. Examples like this are why a reader needs a strong invertebrate biology background in order to appreciate these chimera.
She ends the discussion with another tantalizing mechanism, called the kinetichore reproduction theory. In this process, environmental stress can lead to an additional round of kinetichore - centromere reproduction in an organism's chromosomes which leads to twice as many half-sized acrocentric chromosomes. Fertilization where one donor has undergone this alteration still leads to diploid progeny, but the diversity generated is the engine for adaptive radiation of species.
Obviously, I am not ashamed to say I have bought into her arguments. If I were an academic scientist, I could have a field day testing some of her hypotheses. Instead, I am an industrial biochemist without the necessary time or manpower. That is the power of this book, however. It moves the receptive reader to want to take the bull by the horns and challenge or expand Margulis' hypotheses. She even suggests research strategies for potentially fruitful lines of inquiry.
Drs Margulis and Sagan have written a lightning-rod kind of book that will attract wrath from some, and heartfelt praise from others. If you feel indifferent toward this book, I suggest you reread it with a copy of an invertebrate biology reference book at your side.
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