Acquiring Genomes: A Theory Of The Origin Of Species

by Lynn Margulis, Dorion Sagan

In this groundbreaking book, Lynn Margulis and Dorion Sagan present an answer to one of the enduring mysteries of evolution -- the source of inherited variation that gives rise to new species. Random genetic mutation, long believed to be the main source of variation, is only a marginal factor. As the authors demonstrate in this book, the more important source of speciation, by far, is the acquisition of new genomes by symbiotic merger. The result of thirty years of delving into a vast, mostly arcane literature, this is the first book to go beyond -- and reveal the severe limitations of -- the "Modern Synthesis" that has dominated evolutionary biology for almost three generations. Lynn Margulis, whom E. O. Wilson called "one of the most successful synthetic thinkers in modern biology," and her co-author Dorion Sagan have written a comprehensive and scientifically supported presentation of a theory that directly challenges the assumptions we hold about the variety of the living world.

Genres: Science, Biology, Evolution, Nonfiction, Genetics, Philosophy, Animals

256 pages, Paperback

First published January 1, 2002

About the author

Lynn Margulis (1938-2011) was a Professor of Geosciences at the University of Massachusetts, a member of the U.S. National Academy of Sciences and the Russian Academy of Natural Sciences.

Reviews

[Bill Leach · Rating 4 out of 5]

1 - Darwinism Not NeoDarwinism
- does not agree that mutations are sufficient to allow new species to be created - 99.9% of mutations are deleterious
- symbiosis is the living together of two organisms
- long term stable symbiosis that leads to evolutionary change is symbiogenesis
- in a phylogenetic tree, the fusing of branches is anastomsis
- most animals host symbiotic bacteria and other animals, often depending upon them
- organisms would be better thought of as communities

2 - Darwin's Dilemma
- the Grant's study of Galapagos finches showed environmental pressures producing a 6% change in beaks, but the six species show a variation of 15%
- the minimal unit of life is the cell - all microbes are composed of cells
- the least complex cell, a bacterium, has about 500 genes
- viruses are not alive - outside of a cell they behave as a chemical
- new species are formed by the acquisition of genes
- Stuart Kauffman in his book "Investigations" proposes that thermodynamics is consistent with the formation of life
- life is thermodynamic

3 - Relative Individuality
- life is organized into communities
- the prokaryotes have cells without a nucleus - these are the bacteria
- the eukaryotes have cells with nuclei, and are the protoctists (algae, amoebas, ciliates, slime molds), fungi, plants and animals
- bacteria do not have species - speciation is a property of nucleated organisms
- two examples of eukaryotes that harbor bacteria and cannot live without them

4 - The Natural Selector
- Darwin suggested that species arose not from the physical environment, but from competition with other organisms
- Gaia is the theory of the living planet
- Biota refers to all living organisms
- Gaia is the natural selector

5 - Principles of Evolutionary Novelty
- mutation rarely produces new species - generally produces deficient life forms
- the rapid acquisition of traits be acquisition and integration of former strangers confers immediate selective advantages on organisms
- the only laboratory example of the creation of a new species is the infection of amoebas by bacteria
- organisms gain traits by the accumulation of viruses or plasmids
- long pieces of DNA are acquired by bacterial mating and sexual mating

6 - Species and Cells
- no one has detected the gradual change of one species into another
- animals have one mode of metabolism - oxygen fixation
- plants have two - oxygen and carbon dioxide fixation
- bacteria are the main repository of evolutionary diversity
- bacteria have about 20 different modes of metabolism

7 - History of the Heritable
- examples of associations, including legumes where the bacteria produce heme and the plant produces globin - the resulting hemoglobin is used to transport oxygen away from the nitrogen fixing bacteria
- long story on fungal farming by termites

8 - Gaian Planet
- Vladimir Vernadsky brought the term biosphere into common use, writing a book "Biosphere"
- James Lovelock, a chemist, introduced the Gaia hypothesis which considers life and the environment as a tightly couple single system
- Lovelock recognized that the earth's atmospheric chemistry - mean temperature, alkalinity, and ocean salinity - are regulated by life
- the personification of Gaia is an aid to understanding
- the first bacteria formed 4000 MYA at the beginning of the Archean eon
- the buildup of oxygen started at the Proterozoic eon 2500 MYA - oxygen became plentiful by 1800 MYA
- the Proterozoic eon was the eon of bacteria and protoctists
- animal life formed 540 MYA in the Cambrian eon

9 - Eukaryosis in an Anoxic World
- eukaryosis is the transition from bacteria to eukaryotes
- bacteria are not really speciated - they change over time
- Margulis believes that the proctists that live in sulphur rich mud and in the intestines of animals are representative of the earliest eukaryotes - they cannot metabolize oxygen, they do not reproduce sexually, but they are speciated
- the nucleus probably evolved from "consortia" bacteria - bacteria living with and inside other bacteria
- believes that eukaryotes arose from the merger of an archaebacterium with a eubacterium - the proposed process is detailed

10 - Seaworthy Alliances
- Donal Williamson believes that larval transfer occurs in the larvae of sea life
- among sea life, very different adults can have nearly identical larvae while some closely related adults have very different larvae
- Williamson believes that matings (often sperm over eggs in water) between very different species occurs
- he has witnessed mating of a sea urchin with a cordate
- he posits that larval genes for the moths and butterflies came from the velvet worm (Peripatus) - hence the similarity of all caterpillars
- examples of animals that eat other animals but retain nematocysts or chloroplasts
- the story of the squid Euprymna scoleps which has an organ that obtains and stores a specific glowing bacteria
- Richard Fortey has found evidence that the Olenid trilobites lived in oxygen poor environments and farmed carbon dioxide fixing bacteria

11 - Plant Proclivities
- higher plants and animals cannot get nitrogen from the air, and have had to make use of nitrogen fixing bacteria
- Gunnera maintains colonies of cyanobacteria for fertilization
- all cycads are symbiotic with nitrogen fixing bacteria

12 - Chromosome Dance: The Fission Theory
- closely related species should have similar karyotypes - but not always - the 8 species of muntjacs have chromosome numbers that vary from 3 to 23 pairs
- Neil Todd's Karoyotypic Fission Theory proposes that occasionally all the chromosomes split, forming a new line in an animal
- this can be seen in the lemurs where each family has a different number of chromosomes
- Chromosome fusion is also a process, reducing the number of chromosomes
- the tendency of chromosomes to break, regroup and change probably reflects their past free living states

13 - Darwin Revisited: Species in the Evolutionary Dialogue
- summary
- the rhodospin used in the eye to sense light dates back to archaebacteria that use the same molecule to generate energy from light

The human body is made up of about 6 trillion cells, but there are about 100 trillion bacterial cells on it.

[J.D. Steens · Rating 3 out of 5]

Margulis and Sagan put forward an alternative to a neo-darwinian theory that states that evolution results from random mutations that are acted upon by the environment (natural selection). Random mutations are mostly detrimental to species demise. The real engine of evolution occurs through "symbiogenesis," which means that two or more separate organisms unite and eventually fuse their genetic structures so that formerly independent entities now have an integrated genome that is passed on through the generations. The integration begins at the bacterial level (no cells, but genetic structure). Life rests on the 1800 million years when bacteria lived before there were nucleated organisms. Rather than a line of common descent, the evolutionary tree is, the authors argue, a fusion of once-independent organisms. We are, they emphasize, "composite beings." Organisms they write, "must have a reason to come together," and organisms engage in several different levels of association ("complementary living") prior to the integration of genomes. This in the authors' view supports the punctuated theory of evolution advocated by Gould and others, which argues that major evolutionary change comes in discontinuous jumps, as opposed to gradual, mutation by mutation changes as the neo-darwinians believe.

In a difficult to follow discussion, the authors argue that the evolution of life is ultimately a product of the 2nd law of thermodynamics where complex life forms and systems arise to bring their surroundings into thermo equilibrium. This view stands in contrast to an argument that, at least in the short term, life is an exception to the 2nd law as it concentrates energy for use rather than dissipating it as the 2nd law requires. They write that nature abhors a temperature gradient and builds complex systems (life, ecosystems) to, thereby, reduce "the gradient between the sun and space." In this way, the authors also make it clear that life is not only tied to the 'lowest' microbe level, but to non-life and the physical world.

Margulis and Sagan are critical of the neo-darwinians, the "self-proclaimed evolutionary biologists" who have "dogmatically overemphasized" random mutation, and ignored "the much larger part of the story of evolutionary innovation, the symbiotic joining of organisms." This comes, they believe, from the neo-darwinian "zoocentric" training in only one of the five kingdoms of life, a background that distinctly ignores the tie of animals and ourselves to microbes. The neo-darwinians over use the "old, tired" social darwinist metaphors of "intraspecific competitive struggles." The authors go on to say that their book avoids use of terms such as cooperation, competition, mutual benefit, competitive advantage, which is a terminology "not only fallacious but dangerously so" and is a "philosophical error." Taking on Richard Dawkins directly, the authors say there's no selfish gene. "There's no life in a gene. There is no self." The authors write that the minimal definition of self is a cell, a living system, and they argue that "words like competition, cooperation, and selfish genes" be replaced by meaningful terms such as "metabolic modes (chemoautotrophy, photosynthesis), ecological relations (epibiont, pollinator)...."

While that language is unlikely to enlighten the reading public much, the authors want to move us away from overly simplistic notions about the evolutionary processes and particularly from the paradigm that emphasizes competition and winners and losers. The counter term, cooperation, is also overly simplistic as it suggests that some sort of 'good will' is involved and does not capture adequately the integration of genetic structures over time after several levels of association have occurred. What interests the authors in this book is the "modulated coexistence between former predators, pathogens and their hosts, their shelter and food sources....[where] exploitive relationships may eventually become convivial to the point where neither organism exists without the other."

This is all fair criticism given the authors' perspective. Nevertheless, the authors themselves do not shy away from using common-day language that is rich in implication. They speak of the living cell as the first sign of the "true self". That cell is a composite of formerly independent genetic structures that now give the cell its "character," which is turn gets passed on through the generations. The integration requires "a reason," which introduces the idea of motivation based on 'self-interest' that, in turn, involves "something like free choice." In their description of energy gradients, the authors go even further, suggesting that the "purpose" of life is to facilitate if not expedite the movement to thermo equilibrium. They write, "without invoking any vitalism or mysticism or spiritualism, we can recognize in ourselves a 'purpose.' This purposefulness is an offshoot of the thermodynamic tendency to come to equilibrium. Complex systems, life included, tend to arise in order to bring their gradient-rich surroundings to equilibrium."

It is not so clear that this view of purpose conflicts with Dawkins' selfish-gene theory where the 'purpose' of life is to move genes into the next generation. The authors do not like the selfish gene notion. Again, they say, the gene is not a self, yet Dawkins was perhaps writing more metaphorically, finding a way to describe life's impulse, whether in pre-nucleated cell structures (prokaryotes) or nucleated structures (eukaryotes) to 'self-replicate.' In their book, Margulis and Sagan do not really counter that view and it's possible from their perspective that life's deeper purpose is to self-replicate in order to move cosmic thermodynamics toward equilibrium.

While the book's writing is uneven, moving back and forth from good story telling to more technical-laden information, the authors 'attack'-style language against the neo-darwinians detracts from an otherwise very interesting and thought provoking argument.

[Steve Van Slyke · Rating 3 out of 5]

I went looking for this book after readingPower, Sex, Suicide: Mitochondria and the Meaning of Life by Nick Lane in which author Margulis is mentioned several times, mostly with regard to her theory that mitochondria were originally bacteria that entered into a symbiotic relationship with another, larger bacteria, the first step to developing the first eukaryote and the ancestor of all visible organisms.

I was a little put off by the tone in parts of the book where the authors disparage many of their scientific colleagues, particularly the neo-darwinians such as Richard Dawkins. I understand that science involves criticism and challenges to accepted theories, but there is a diplomatic way to do that rather than accusing others of being ostriches who fail to consider new ideas and are oblivious to other disciplines.

Nevertheless, it is always healthy to have competing views, skeptics and an open discussion of all possible answers to an important question. But it seems the authors aren't satisfied to have their theories integrated with others as part of the answer—they want theirs to be the primary if not whole answer. It seemed unbecoming.

I can't remember reading a book whose foreword refutes major aspects of the book itself, saying that some parts are outright wrong, warning the reader to be wary. But perhaps because the foreword was written by famed biologist Ernst Mayr, and given that he does praise many if not most aspects of the book, they felt it was worth the pain. It is worthwhile to read his foreword a second time after you finish the book.

To a lay reader like myself, the book certainly gives one a pause to consider that evolution may not be as fully understood and as tidy as we thought. Speciation by random mutation and differential survival may not be the only rule: genome acquisition and symbiogenesis may play an important role. But just how important, and exactly how, is a subject of ongoing debate as much as natural selection was during Darwin's time. Stay tuned for more information

[Shea Mastison · Rating 3 out of 5]

I first became aware of Lynn Margulis while reading Michael Behe's "Darwin's Black Box;" I was heavily skeptical when initially grabbing this, because Behe uses her as a reference to "prove" evolutionary theory is heavily disputed in the scientific community.

However, this book was much more impressive than what I looked to credit it for; while I am a bit suspicious concerning symbiogenesis, I recognize that it is an actual scientific theory.

There were a few moments when the author argues that if symbiogenesis is one of the prime drives behind speciation, then we need to adopt an understanding as cooperation more than competition as an evolutionary factor--the sentiment in which this was expressed was a bit strange: almost as if the author was arguing humanity would be better of socially if it were true and well known. Which isn't exactly how I would try to argue for a competing theory to genetic variation.

The book is a bit dry, but if you're into popular science, check it out.

[Ann · Rating 4 out of 5]

This book blew my mind. Margulis has an innovative theory that symbiosis drives speciation, and her collaboration with her writer son makes the explanation lucid (although at least a college intro course in biology is recommended background).

[Surabhi · Rating 4 out of 5]

I recall reading in school that mitochondria originated from bacteria that were taken up by eukaryotic cells. It was just a small snippet amidst other detailed theories. I remember thinking it was bizarre and dismissed it immediately as mere speculation.

So, when I found this book, I was intrigued and wanted to know more. I am glad that I did.This was an insightful and fascinating read that explored the complex processes by which genetic information is acquired, passed down, and expressed within our cells.

Throughout the book, the author explored the many different mechanisms by which genes are expressed, including epigenetic modifications, alternative splicing, and gene duplication. She also examined the ways in which genetic information can be acquired and exchanged between different organisms, such as through horizontal gene transfer and viral infection.

What I relished the most were the real-life examples and case studies she used to illustrate her points like the stories of scientists who have made groundbreaking discoveries in the field of genetics, as well as examples from nature that demonstrate the incredible complexity and diversity of genetic processes.

A must-read for anyone interested in genetics and the workings of the human body. With its engaging writing style, insightful analysis, and real-life examples, it is a fascinating and informative journey into the world of genetics and the incredible processes that govern our very existence.

[Fleece]

"I'm finished" as in I'm finished with this book. Got to page ninety and had to ditch it because it was terrible; not the idea, we've been taught symbiogenesis was how chloroplasts and and mitochondria were acquired in plant and animal cells, but i feel like they didn't really connect symbiosis and symbiogenesis- explanations were skimpy and examples didn't go as in depth as I'd like.

Other stuff that annoyed me: defining terms after the fact, 'breathe' used instead of 'uses as electron acceptor' because they didn't bother explaining redox reactions, a weak presentation of thermodynamics, and so on. Most of it was presentation of ideas that weren't backed up or explained.

[Miles · Rating 4 out of 5]

I have to preface this review with an important admission, which is that my background in popular science literature has definitely not prepared me to fully comprehend, let alone criticize, the finer scientific arguments presented here. There are whole sections of this book that are inaccessible to me due to esoteric vocabulary alone. Margulis and Sagan appear to have written an intelligent book that is supported with a fair swath of responsible research, but I'm far from able to detect the points where their reasoning fails to cash out or their evidence is unsuitable, if in fact any such infractions exist. That said, I enjoyed the book very much. It was definitely a departure from the basics of evolutionary theory as I have come to know them, but I didn't run into too many red flags that made me think Margulis and Sagan were arguing anything that should be relegated to crackpot territory. And while they are certainly arguing against a certain mainstream view (referred to as "neodarwinism"), they also didn't seem to be rejecting any essential, nonnegotiable evolutionary concepts.

The idea of acquiring genomes as the primary impetus for biogenesis is entirely new to me, and I find the whole suggestion fascinating. While I did sometimes got lost in the more technical bits, Margulis and Sagan did a good job of making their general points accessible. Apparently 20th century science didn't take into account the crucial role that bacteria play when it comes to influencing Earth's ecosystems and generating new species, so the authors are trying to make up for what they see as a major deficit in evolutionary thinking. Their holistic approach generally resonates with me, as I enjoy thinkers who try to draw connections between different systems of thought and academic disciplines. The problem with this method, however, is that it's easy to create patterns where none exist, and sometimes there are few people with the requisite expertise to properly analyze and reject any missteps, if they exist. So I read this book with a kind of cautious enthusiasm, with an emphasis on enthusiasm. Many of the ideas that are championed in this text, such as the Gaia hypothesis, are worthy of consideration even if they prove resistant to traditional empirical scrutiny, at least in my view. So I tried to me open-minded here, but not so open-minded that my brain would fall out.

My favorite part was the suggestion that life's purpose is to build complex systems designed to thwart the second law of thermodynamics with ever-increasing efficiency, which is actually a view I've ascribed to since I wrote a paper about entropy in high school. It is really nice to see that notion fleshed out and legitimized by members of the scientific community. Viewing myself and my greater biological community as unified through a defiant resolve to persist and propagate despite the fact that individual energy systems invariably degrade into inert states is both empowering and spiritually gratifying for me.

Even though I liked the book overall, there were a handful of questions that I didn't feel were addressed properly by the end. The authors provided lots of examples of how small creatures can acquire the genomes of other organisms to precipitate speciation, but I was surprised that they failed to offer examples of how this happens (or might have happened) with larger mammals, such as humans (the one exception is that they refer to the cow's rumen a couple times, but never in much detail). I was left wondering how, for example, symbiogenesis could have produced humans from apes, or dogs from wolves. Even if they were purely speculative, I would have appreciated some suggestions about how genomes are or have been acquired by organisms that play a larger role in my life. I don't think this necessarily discredits the authors or this book, but it's certainly something I'd bring up if I had the chance to sit down and chat with Margulis and Sagan.

Another issue is that I remain unconvinced that terms like "cooperation" and "competition" aren't useful when talking about evolution, even if we accept the basic principles of genome acquisition. The authors repeatedly mention that such terms don't really apply to their particular interpretation of evolution, but I just don't think their arguments really support that claim. In fact, Margulis and Sagan describe symbiotic relationships as often resulting from physical conflicts between organisms that, over time, learn to work together instead of trying to kill one another, thereby acquiring one another's genomes and sometimes giving birth to a new species. It seems to me that the concepts of cooperation and competition are very useful in describing this development. It's just that we need to realize that such terms are fluid––organisms that once competed can become co-operants, and vice versa. I think Margulis and Sagan really just want to revise how we think about these words, not do away with them altogether. Indeed, I find it laughable to think we'd ever have a theory of evolution in which cooperation and competition weren't incorporated, at least at some basic level.

Despite my few complaints, which I'm not even sure make any sense given that I'm not a scientist, this book provided the kind of shift in perspective that proves more and more rare as I continue the process of self-education. I found myself realizing that I think humans are, if only in a metaphorical if not a literal sense, being "acquired" by nascent technological entities and other super-organisms, such as nation-states and corporations. Just as larger beings can encapsulate microbes and adapt them to serve specialized functions, thereby prioritizing the needs of the whole over and above the needs/desires of the individual microbes themselves, I believe super-organisms are currently enacting the same process with populations of individual humans. Maybe this has always been true in some sense, but I feel that the process is accelerating at an unprecedented rate due to the increasing power of technology and the far-reaching consequences of globalization. It would be arrogant to suggest that I know where it's ultimately all headed, but I find it harder and harder to envision a future in which the concerns of individual humans beings are of much importance. And while that thought scares me quite a bit, I'm not convinced that such a world would be evil or bereft of significance and value. Maybe that's just how life develops, whether we like it or not.

[Solveig · Rating 4 out of 5]

I read this book for a science book club; unlike some of the books we have read it can't be accused of being light on the science. This is one of the good points of the book: it provides numerous examples of its main point that evolutionary variation appears due to symbiogenesis, and these examples come with references. The main bad point of the book is that it is too defensive; I don't work in the field of evolutionary biology, so don't knoe if the defensiveness is understandable from a science historical point-of-view, but I found it grating. It was as if the authors weren't confident enough that their thesis would stand on its own merit, but had to resort to smearing the 'opposition'. In the less polemic parts of the book, the authors acknowledge that random mutation occurs, and can have benefitial effects. However, in the main they tut-tut the idea; from my experience of the much cleaner science of physics, the true explanation of any effect is usually not as simple as just one cause. I imagine this is even more prevalent in something as complex as biology.

[M · Rating 2 out of 5]

Margulis (and Dorion Sagan) have a groundbreaking theory about evolution, namely, that new species arise not from lots of minor mutations, but from the acquisition of entire genomes like when a colony of bacteria refuse to be digested and instead survive in the host organism as symbionts. They make their scientific case in this book, but I was hoping it would be a little more geared to the layperson. Specifically, I wish it had more examples of species we are all familiar with and speculation on how they might have sprung from another pair of species. The authors would probably chide me for being mammal-centric, but really, for most of us readers new strains of bacteria fail to capture the imagination.

Interesting side note: Margulis and this theory were mentioned by Luca Turin as an example of radical scientific theories being proven right in The Emperor of Scent, which I was reading concurrently.

[Julie M · Rating 4 out of 5]

This is my favorite book. If you want to be wowed by your own existence, read this book. I think about this book anytime I catch myself thinking that I'm more important than anyone else--which happens more often than I'd like to admit.

It's hard to be a narcissist when you realize that your body and the entire living world around you are just big groups of mutated, evolved bacteria that smooshed together billions of years ago because they knew it'd help them survive. If mutated bacteria knew they had to work together to survive, how has 'the most advanced species' not done the same?

Cutest excerpt: "Apparently 'counter-illumination' --a kind of camouflage-- is the reason. Predators from below or potential prey see night sky instead of the tasty little squid belly when they gaze at the mature illuminated squid." (on the luminous squid Euprymna scoleps)

[Peter · Rating 4 out of 5]

Lyn Margulis, ever the iconoclast, takes on the neodarwinists. In this book, she presents a very compelling case for the role of symbiosis in the origin of new species. She brings together the work of many to show the importance of the acquisition and integration of new genomes by symbiotic merger. Margulis is a good and careful writer, but this is a difficult subject for a "popular" science book. All terms are defined and there is a good glossary. It's a fascinating idea, and she may well be right, as she has been before.

[Eric · Rating 5 out of 5]

A must-read if you are interested in moving beyond a neodarwinian view of evolution, in which random mutation is purported to lead to all sorts of miracle lifeforms. These iconoclastic authors present what seems plausible evidence from a scientific viewpoint for alternate mechanisms of the advent of new species. Absolutely fascinating.

[Adrián · Rating 4 out of 5]

Un libro sobre evolución con una idea poco enseñada sobre la evolución de las especies. Se replantea las definiciones de especie, y las teorías de evolución neodarwinistas, y defiende por qué el equilibrio punteado es un mejor modelo que el gradualismo. La parte sospechosa es donde se tratan las ideas casi místicas sobre la biosfera como un super-organismo llamado Gaia.

[Wendi Lau · Rating 4 out of 5]

Little hard for me to follow but very interesting and timely. Bacteria and virology are becoming more forefront in science discussions and development. The authors insist that biologist should become versed in more life science fields to better understand their field. Using microbial life as the model and base for species development makes total sense.

[Becky · Rating 3 out of 5]

I don't buy all the theory Margulis is selling, but it's an interesting take.

[Nola · Rating 2 out of 5]

Acquiring Genomes is an explanation of how evolution proceeds mostly by acquisition of genomes, rather than by inheritance of beneficial mutations. The tone of the first chapter gets too heated when Margulis criticizes Neo-Darwinist terminology. For me, this chapter went off the cliff and then put in these two sentences advocating clarity in language, which I was totally unable to understand:
“So many current evolutionary metaphors are superficial dichotomizations that come from false clarities of language. They do not beget but preclude scientific understanding.” The angry tone diminished after that, but I still had the underlying sense of having been scolded without understanding why. There are several interesting points made in the book. These include
• New species come about through acquisition of genomes, mostly by taking up bacteria, and having them become a permanent part of what would then be a new species.
• Bacteria, according to Margulis and Sagan do not have species. Their definition of species is organism that have the same genome. Ernst Mayr’s definition of species is “two organisms belong to the same species if they recognize each other, can mate, and can produce fertile offspring.”. Margulis and Sagan agree with this definition, but say it only applies to plants and animals. Since any bacteria can pass genetic material between themselves, which is what Margulis and Sagan call “sex”, it doesn’t make sense to use Mayr’s definition for bacteria.
• Living organisms obey the laws of thermodynamics by decreasing gradients. Life developed as a means of reducing chemical and energy gradients.
• Successful matings between very distantly related animals may have occurred infrequently throughout evolutionary history, leading to new larval types.
Overall the book is reasonably understandable if you pay close attention. However, there are so many examples that an overwhelming number of researcher’s names and institutions come up throughout the book. These authors are obviously familiar with the work of many different scientists worldwide. There are also a lot of scientific terms. I was disappointed that the glossary in the back did not contain any of the terms I looked up even though it had terms that were extensively defined in the text. It seems like sporodochia, nematode, hypermastigote, eukaryosis, among others, could have been included.

[Nate Gaylinn · Rating 5 out of 5]

A striking argument for a new theory of evolution, with extraordinary biological evidence.

This book makes the case for a controversial yet compelling theory of evolution. The first two thirds cover the necessary background in biological concepts, evolutionary theory, and the history of life on this planet needed to present the case. The last third is a laundry list of bizarre examples from nature that seem to contradict the status quo, as well as stories of scientists and developing theories that better explain the evidence and could serve to update our overall picture of evolution. That last part is a bit more technical than the rest, but the big Latin words are mostly just names, and the examples of strange symbioses are spectacular.

The greatest weakness of this book is that it overreaches a bit, and its underlying theory is still under-developed. There's a strong case here that symbiosis and other related phenomena played a big role in evolution. But how big? And why is symbiosis the critical factor? What does it mean for a single individual to "have multiple genomes"? And what about the fascinating example of chromosome counts at the end? That's not symbiosis, but is it an example of a more general pattern, of which symbiosis is just one example? The greatest strength of this book is that it raises such questions, and makes them sound relevant, but until we start answering some of them it's hard to say how much the central claim in this book is true.

A quick, fun read with a mind-expanding perspective on the weirdness of microbiology and what it might mean for evolution as a whole. I agree with the authors: understanding early life on this planet and how different it is from us is critical to understanding what life is, what we are, and how it all came to be. No definitive answers here, but a fantastic window on an under-appreciated corner of the scientific world.

[Molsa Roja(s) · Rating 5 out of 5]

Un llibre absolutament meravellós sobre la biologia evolutiva i la microbiologia. És increible el saber de Margulis en temes desconeguts no sols per la majoria de la població, sinó també per bona part de la comunitat científica, fins i tot per biòlegs. En aquest llibre, Margulis porta més enllà la teoria lamarckiana de transmissió de caràcters adquirits i la completa amb els dubtes que el propi Darwin tenia sobre el procés real evolutiu, donada la falta de fòssils que mostrin un canvi gradual en les espècies. I és que aquest canvi gradual no és tal, sinó un salt quàntic (tal i com s'hi referiria Schrödinger). Si Schrödinger pensava que aquest salt quàntic en la vida era degut a mutacions genètiques, Margulis demostra en primer lloc que la majoria de mutacions són perjudicials per la vida i són ràpidament eliminades; en segon, i més important, demostra que aquests salts poden ser explicats a partir de l'adquisició de nous genomes, a partir de la simbiogènesi. Així, les bactèries i les seves increïbles capacitats combinatòries, no directament reproductives sinó de manera transmissió d'informació, són el gran vehicle del canvi: semblaria que tota bactèria, inclassificable com a espècie donada la seva variabilitat, ha estat simbiòticament associada. I que, de fet, la vida mateixa sorgeix de les arqueobactèries, vida entesa com a inici de l'especiació, com a naixement de la cèl·lula eucariota. La llista de bactèries que conviuen amb nosaltres, amb la majoria d'animals superiors, és incomptable: l'adquisició d'aquestes, la fusió dels nostres genomes, ens ha portat on som. Un anàlisi més profund, ens porta a detectar adn bacterià en gran part dels organismes. Així, els bacteris i la simbiosi serien realment el motor de l'evolució.

[Allen · Rating 4 out of 5]

Lynn Margulis is the ex-wife of Carl Sagan. She wrote this book with her son, Dorian Sagan. The writing leaves something to be desired but the ideas are brilliant. The ideas brought forth in this small book were eye openers for me. Obviously, I've got to go backward and find more by Lynn Margulis. Not only are her ideas fresh but she opens up the idea to the reader that what we accept as gospel might just have been the result of academic laziness, a bad habit allowed to stand because no one had a mind to question and take the facts in another direction. She puts forth the idea of evolution by symbiogenesis. It makes so much sense. I never liked the idea of evolution by random mutation; the idea that not only would the strand of RNA vary due to random mutation, but that the mutation would be an improvement? That never rang true for me. What are the chances? Margulis postulates that evolution in large measure happens because of bacteria. Bacteria exchange whole genomes readily. Species can ingest bacteria but not digest it. They live in a symbiotic relationship. If the relationship is a good one the DNA of the bacteria is acquired by the host into its own DNA.

[Samir Firdovsioglu · Rating 3 out of 5]

The book is an important book that shows incompleteness of the theory of evolution. Lynn Margulis and her son basically tell us that:
- a common ancestor is wrong, there were more than one ancestor.
- random mutations cannot produce new species or organs
- darwinian gradualism/ gradual evolution is false
- there is a dogmatic adherence to basic tenets of neo-darwinism among the evolutionary biologists.
But the book is riddled with a lot of unexplained and unsubstantiated claims. The authors claim that the Earth acts like a gigantic cell and becomes a natural selector, which sounds like a replacement for God. They do not explain how apes can transform into homo sapiens through the fission of chromosoms. What they claim should be testable. Fission of chromosoms can be done in laboratories, but yet to be seen.

[Kiko León · Rating 4 out of 5]

A Lynn Margulis deberían haberle dado el Nobel por su teoría simbiogenética tan bien explicada en este libro. Aquí trata el fenómeno de la especiación y propone una teoría elegante y bella para el enigma del origen de las especies. Describe procesos fascinantes, muy curiosos, que abrirán la mente del lector al fenómeno de la vida.
Estoy de acuerdo con lo que advierte Adriático en otra de las reseñas a este libro en castellano: plantear a Gaia como a un metaser del que nosotros somos orgánulos contiene un peligro de todo organicismo de convertir a un ente real -nosotros- en una pieza sacrificable para bien de un ser hipotético y, al fin y al cabo, abstracto: Gaia. Pero da igual cuál sea nuestra postura sobre esa controversia, es justo decir que éste no es un libro sobre la Hipótesis Gaia sino sobre la simbiogénesis en la especiación de los seres vivos.
Margulis repudia al neodarwinismo y si no nos dejamos arrastrar por el, en mi opinión, diálogo de besugos ideológico que se ciñe en torno al darwinismo, este es un gran libro de ciencia. Para mí un hito en la biología.

[Bon Miu · Rating 5 out of 5]

Thrilling and exciting, very cool ideas, synthesising multiple disciplines toward an appreciation of novel evolutionary theory; and at the very least, that evolution is not nearly fully understood and requires more work deliberately wary of neodarwinist hubris. Beyond this, also provides insight into the limitations of today's segregated sciences. A privilege to read but highly inaccessible to those not versed in scientific jargon!

[Mónica · Rating 5 out of 5]

Muy interesante libro donde se nos explica el origen de las especies y como éste no fue en sí mismo concurrente con el origen de la vida sino que ocurrió mucho más tarde, en el Eón Proterozoico.
Deja ideas como los ejemplos de evolución por simbiosis desconocidos por mí, que la selección natural perpetúa pero no crea, etc.
Libro científico pero que se lee con facilidad pues es sumamente interesante.

[Miguel · Rating 2 out of 5]

No tengo ni idea de si la hipótesis es correcta o no, pero no me ha gustado cómo lo presenta. Divaga, pasan las páginas y nunca termina de llegar a explicar algo. Los ejemplos aparecen ocasionalmente, pero no están aparentemente relacionados.

Y, además, las notas que va dejando contra otros modelos de evolución rozan el insulto a sus defensores. Pueden ser correctas o incorrectas, pero esos mensajes suenan a desprecio.

Es una pena, empecé el libro con verdadera ilusión.

[Harry Gardner · Rating 5 out of 5]

There are a few things that Lynn Margulis states that are controversial--the notion of the world as one interconnected 'natural selector'--but some of her arguments in explaining speciation through symbiogenesis are phenomenal. This book is worth your time if you are interested in evolutionary biology and the controversies that underlie it.

[daniel · Rating 5 out of 5]

Kellie

[Iliana · Rating 5 out of 5]

So many sticky notes... Followed 9B exactly, understood 80% which felt really good.

[Juan Acero · Rating 4 out of 5]

Ha quedado un poco anticuado en algunos aspectos, pero sigue siendo un libro muy interesante.

[Ellen · Rating 3 out of 5]

I wound up kind of skimming the second half, but it's pretty provocative and persuasive