Synopsis
Although Charles Darwin's theory of evolution laid the foundations of modern biology, it did not tell the whole story. Most remarkably, The Origin of Species said very little about, of all things, the origins of species. Darwin and his modern successors have shown very convincingly how inherited variations are naturally selected, but they leave unanswered how variant organisms come to be in the first place.In Symbiotic Planet, renowned scientist Lynn Margulis shows that symbiosis, which simply means members of different species living in physical contact with each other, is crucial to the origins of evolutionary novelty. Ranging from bacteria, the smallest kinds of life, to the largest—the living Earth itself—Margulis explains the symbiotic origins of many of evolution's most important innovations. The very cells we're made of started as symbiotic unions of different kinds of bacteria. Sex—and its inevitable corollary, death—arose when failed attempts at cannibalism resulted in seasonally repeated mergers of some of our tiniest ancestors. Dry land became forested only after symbioses of algae and fungi evolved into plants. Since all living things are bathed by the same waters and atmosphere, all the inhabitants of Earth belong to a symbiotic union. Gaia, the finely tuned largest ecosystem of the Earth's surface, is just symbiosis as seen from space. Along the way, Margulis describes her initiation into the world of science and the early steps in the present revolution in evolutionary biology; the importance of species classification for how we think about the living world; and the way “academic apartheid” can block scientific advancement. Written with enthusiasm and authority, this is a book that could change the way you view our living Earth.
Reviews
Gracing her tale with personal touches and with lines from the poems of Emily Dickinson as chapter headings, Margulis describes the development of her theory of symbiosis and ponders how it relates to the Gaia concept of a living Earth. "No species existed before bacteria merged to form larger cells including ancestors to both plants and animals," she writes. "The permanent incorporation of bacteria inside plant and animal cells as plastids and mitochondria is the part of my serial endosymbiosis theory that now appears even in high school textbooks. But the full impact of the symbiotic view of evolution has yet to be felt. And the idea that new species arise from symbiotic mergers among members of old ones is still not even discussed in polite scientific society." The Gaia concept is that aspects of Earth's atmospheric gases and surface rocks and water are regulated by the growth, death, integration and other activities of living organisms. Gaia, Margulis says, "is a convenient name for an Earthwide phenomenon: temperature, acidity/alkalinity, and gas composition regulation"through the series of interacting ecosystems that compose a single huge ecosystem at Earth's surface. How do symbiosis and the Gaia concept relate to each other? Greg Hinkle, once Margulis's student and now a professor at the University of Massachusetts, provides an answer that Margulis likes: "Gaia is just symbiosis as seen from space."
Let's hear it for the bugs not your creepy-crawlies, but bacteria, the be-all (and possible end-all) of life on Earth, according to Margulis. Here she describes the once radical theory that cells have incorporated bacteria to mutual advantage and uses that as a springboard to summarize a still more radical theory of how species evolve. She calls it serial endosymbiosis theory (SET). It is now conventional wisdom that the energy-producing mitochondria in animal cells were once free-living bacteria. Indeed, they have their own genesdifferent from nuclear DNA. Margulis provides many examples of fruitful symbioses, including sexual union itself as the merger of sperm and egg cells. According to SET, there are successive steps or mergers that led to multicellular life forms: In steps one and two the oldest bacterial formsthe non-oxygen breathing ``archaebacteria'' found in deep ocean ventsmerged with swimming bacteria two billion years ago to form the nuclear heart of animal, plant, and fungal cells and provide the cilia for swimming. Later steps introduced a third partner able to breathe oxygen and added the ability to engulf and digest food (phagocytosis). The last step involved engulfing yet another bacteriumbut one these various new forms of life could not digest: bright green photosynthetic bacteria. The bone of contention here is the origin of ciliated cellscritical to evolution for their vital role as sperm tails, among other things. Margulis has a theory about their origin, but as they say, more research is needed. Margulis's theory also dictates a change in taxonomy to five kingdoms: bacteria at the base, then ``protoctists'' (algae, slime molds, ciliates) next, and then animals, plants, and fungi. Finally, she defends Lovelock's Gaia theory, which she interprets to mean that enormous interacting ecosystems on Earth achieve homeostasis rather than that the planet is in the hands of some benign Mother Earth. This is vintage Margulispersonal, autobiographical, passionate, argumentative, at times over the top, but full of ideasat least some of which, in the past, have proved to be right. -- Copyright ©1998, Kirkus Associates, LP. All rights reserved.
From the origin of life to the classification and phylogeny of living organisms, from a discussion of GaiaAthe belief that Earth operates like a living beingAto a discussion of the underlying reasons for sex, iconoclastic biologist Margulis (coauthor, What Is Sex?, etc.) takes on many of the big questions in biology in this small, rambling and informal tract. In a book that is part autobiography and part biological primer, MargulisAthe scientist most responsible for the theory that animal and plant cells originally arose by combining with simple bacteriaAadvances the idea that a large part of organic evolution can be explained by symbiosis, "the living together in physical contact of organisms of different species." Rather than convincing readers of this theory, however, she seems content to lavish most of her attention on basic biological concepts. While Margulis conveys a sense of the wondrous and intricate origins of life, many of the issues she touches upon here are more clearly and comprehensively dealt with in her other works. 11 b&w illustrations.
Copyright 1998 Reed Business Information, Inc.
For 30 years, the Gaia theory of life on Earth has remained vital, dynamic, and controversial. One of its leading advocates provides a synthesis and overview of the current status of the theory, plus a few important new ideas of her own.
Copyright 1999 Reed Business Information, Inc.
Microbiologist Margulis has championed for decades her theory that new species originate not just in genetic mutation but in symbiosis as well--the merging of two separate species. In this addition to Basic's Science Masters series, Margulis combines bits of autobiography (she was Carl Sagan's first wife) with microbial evidence of her theory; the latter includes the constituent organelles of the cell, such as mitochondria. She then slants into the arcana of taxonomy, with a history of how the current five kingdoms of biology overthrew the old plant-animal-protozoa troika. Margulis' argument that symbiosis underlies the "Gaia" outlook typifies her forceful style, which should energize biology students. Gilbert Taylor
"About this title" may belong to another edition of this title.
