Symbiotic Planet: A New Look at Evolution [Paperback]

Some years ago, Margulis promoted a new concept in evolution. Complex life developed from the merging of microbial forms of life. Elements of the cell such as mitochondria, chloroplasts and other organelles came from small, simple lifeforms invading larger cells. The idea was a long time in gaining acceptance, but is now part of conventional evolutionary texts. In this book, she expands her earlier work with some accounts of her life as a scientist and wife of Carl Sagan. She also goes beyond her earlier work to advance a new thesis on the accelerator of evolution - sex. While many of her ideas are presented in more detail elsewhere, this book is a good, quick introduction to fuller accounts of her thinking.

Margulis is an innovator - forceful in imparting her ideas. She portrays herself as a rebel from early in her career, arguing here that she was sceptical of "genes in the nucleus determin[ing] all the characteristics of plants and animals." Her misgivings received scant support, however, without a replacement thesis. She found one in symbiosis - the association of multiple organisms. It took many years of investigation, including initial rejection of her attempts to publish, before the idea of SET [Serial Endoymbiosis Theory] found acceptance. So much attention had been focussed the DNA in the cell nucleus that organelle structure and function had been essentially overlooked as irrelevant. That these organelles might have been independent organisms at some point was too novel. Her account of the struggle to gain recognition is related as one of dogged persistence, nearly devoid of outside support .

Moving through an interesting discussion of life's origins, she dismisses the notion that forms of nucleic acids arose before simple cells. She finds the natural occurence of lipids [fats] as the more likely precursors of complex life, with RNA and DNA arising as a way to give these fat globules more survival ability. As with her earlier thesis, this one will generate controversy, something Margulis seems nutured on.

Her proposal about the emergence of sex will come as a surprise to most readers. In a word, she suggests sex resulting from cannibalism. In Margulis' view, certain microbes under stress, notably the absence of food, turned on each other for survival. The cannibalism was not always fully consummated, she suggests, but the beginnings of mixing genetic material was begun in the process. Incomplete cannibalism could lead to the formation of a new, more complex organism. If this process occurred often enough within a compatible group, the new organism, obviously larger than its predecessors, would be more fit to compete.

In conclusion, Margulis makes a strong case in favour of James Lovelock's Gaia concept. This might have been a non-sequitor in the hands of someone less able to deal with novel ideas. Margulis stresses that Gaia has been mistakenly viewed as Earth's biosphere acting as a single organism. She argues that Gaia really means a global network - a "system of organisms." The Gaia concept means the elements of the "system" are tightly entangled and extinctions weaken the structure. If the extinction rate exceeds the rate of recovery the system is endangered. It's interesting to note in light of her definition that the Gaia website still refers to it as a "superorganism," not a "system of organisms." This disparity doesn't detract from Margulis' presentation, which is admirably presented. She offers enough graphic support for the text to clarify or enhance her themes. In all, this is a fine mind-opener in thinking about the development of early life. Readable by anyone interested in life's history and processes.

Lynn Margulis is Distinguished University Professor in the Department of Geosciences at the University of Massachusetts, Amherst. She is a prolific author, writing mostly about the early stages of life on Earth, particularly with regard to microbial evolution and its contribution to organelle heredity in multicellular organisms. Throughout her long career she has never ceased to challenge the views of the scientific establishment of the day, doggedly persuing every avenue of enquiry and bringing common sense thinking (invariably backed up by good, solid scientific investigation) to a number of controversial fields of study.

She is probably best known for her theory of serial endosymbiosis -- the process of successive fusion of genomes through the formation of countless, novel symbiotic consortia of microbial organisms. Since its formulation over 40 years ago, this theory has always threatened the central tenet of neo-Darwinism -- that genome alteration occurs principally through random mutation -- and getting it accepted has been a long, up-hill struggle. Lesser mortals would probably have given up trying long ago. Professor Margulis has also worked for many years on the development of a 5-kingdom taxomony which has eventually been accepted as a more appropriate replacement for the previously long established (but hopelessly inadequate) division of all living things into just plants and animals. One cornerstone of that work is the recognition of the place of microbes (bacteria and protoctists) as well as fungae as living kingdoms every bit as distinct as plants and animals, and occupying crucial places in the evolutionary scheme of things.

In addition to fighting the unfashionable microbial corner in life-sciences thinking, Lynn Margulis has also been active at the other end of the scale, contributing to the development of the Gaia concept. Originated by James Lovelock, this posits that the interactions between the Erath's bioshere, hydrosphere, lithosphere and atmosphere act as one vast self-regulating system.

In "The Symbiotic Planet: A New Look At Evolution", the author provides a summary of these areas of her life's work and explains the connecting threads that link them all. Along the way, she provides some interesting asides on both her personal scientific journey and the difficulties involved in overcoming long-established prejudices (both within and outside the scientific community). As such, this book forms a useful introduction to the work of Lynn Margulis.

In spite of its complex and specialist subject matter, the book remains eminently accessible even to the lay reader. For many, this will be a quick and light read, which, whilst uplifting and inspiring in its outlook (and potentially eye-opening in its content) may nevertheless feel to lack substance to those looking for an in-depth treatment. For that, you'll need to turn to other books, mostly by the same author. Her "Early Life: Evolution on the PreCambrian Earth" (written in conjunction with Amherst colleague, Michael Dolan) forms a useful and technically detailed account of current state of thinking on the earliest phases of microbial evolution, whilst "Acquiring Genomes: A Theory of the Origins of the Species" (co-authored with her eldest son, Dorion Sagan) provides an in-depth study of Serial Endosymbiosis Theory. Details of the five-kingdom approach to the taxonomy of living things can be found in "Diversity of Life: The Illustrated Guide to the Five Kingdoms". The definitive text regarding the Gaia Concept remains James Lovelock's "Gaia: A New Look at Life on Earth". But if all you want is a quick overview of all of these, this book will do just fine.

Decent easy read. Introduction to the scientific ideas of Lynn Margulis. She pays due respect to the scientists who have helped either by anticipating or critically commenting upon her thesis of symbiosis .She explains how the idea of the symbiotic origin of the eukaryotic cell was formulated.She is honest about those aspects of her theory which remain controversial and have failed to receive widespread support. Worth reading as an introductory text. If only it was two or three times longer.