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What is Life?

by Lynn Margulis and Dorion Sagan.
University of California Press: Berkeley & Los Angeles, 2000.
320 pp., illus. color + b/w, $35.00.
ISBN 0-520-22021-8, paperback.
Reviewed by Wilfred Niels Arnold, Professor of Biochemistry, University of Kansas Medical Center, Kansas City, KS 66160-7421 U.S.A.
E-mail: warnold@kumc.edu


Dr. Margulis is well recognized for her working hypothesis on the origin of organelles within eukaryotic cells; namely that inter-cellular entities such as chloroplasts and mitochondria began as cyanobacteria and respiring bacteria respectively, and that symbiotic origins for new life forms were important aspects of evolution in the Darwinian tradition. Dorion Sagan has published several 'science for the citizen' books with provocative titles ranging from "What is sex?" to "Garden of Microbial Delights." Together they now bring us "What is Life?" which foreword contributor Niles Eldredge promises will equip the reader with an understanding of the living world. This paperback edition stems from a book released by Simon & Schuster five years ago.

The essence of the senior author's major contribution to the primary literature, symbiogenesis, is covered in chapter 5, "Permanent Mergers." There are nine chapters in all, with catchy titles such as "Once upon a planet" and "Flesh of the earth." Many of the items under discussion are blessed with animus. This is most evident in chapter 3, entitled "Lost Souls," which starts with a review of ancient concepts about the whistling of the wind, changing phases of the moon, and so on, and ends with an embrace of James Lovelock's "Gaia hypothesis." The latter claims that life manifests itself on a planetary scale, based on atmospheric, astronomical, and oceanographic evidence. The authors relate Gaia to "over thirty million types of beings, descendants from common ancestors, and members of five kingdoms that produce and remove gases, ions, and organic compounds. Their interacting activities lead to modulation of Earth's temperature, acidity, and atmospheric composition." They get full marks for courage in taking on a high level of complexity. Their arguments are full of fresh metaphor and analogy, but one is sometimes left wondering how much this advances the field in the absence of measurable data.

There are 31 color plates as a group in the middle of the book. These are all of inherent interest, well chosen, nicely reproduced on quality paper, and function as a freely standing entity. They start and end with pictures of the earth from outer space and encompass all sorts of living organisms. The 18 b&w illustrations and two tables are useful. They include schematics of the natural histories of various species.

The ten page glossary is new to this edition, consists of 161 items, and from its tenor I tried to gauge the intended audience: a few extracts follow. "ATP: adenosine triphosphate, a phosphorous-, carbon-, nitrogen-, oxygen-, and hydrogen-containing ring compound that is universally used by life to store energy in its phosphate bonds. Cellulose: a sugar-rich compound of cell walls of plants and some protoctists. Chitin: a sugar-rich, nitrogen-containing compound of cell walls of fungi and insect exoskeletons. Cross walls: cell walls. Cytoplasm: the fluid of cells outside their nuclei." Readers without any science training are surely still in doubt; others will wonder why they bothered looking up a term. The authors were apparently convinced that their patrons would be incapable of contemplating chemical structures. This is not an experience I share. The average citizen has no difficulty 'seeing' the differences in the chemical structures of cellulose and chitin when they are depicted as chains of different sugar residues. Why are so many publishers "afraid" of chemical and physical symbols?

At the end of each chapter the authors ask, "So, what is life?", which form a series of summary statements. Accordingly, the final statement, in the epilogue, is a bit anticlimactic, " ... we can ask with curiosity but can answer only tentatively and with humility the question of what life is, hoping, with you, that the search continues." Margulis and Sagan acknowledge that the revival of Schrūdinger's inquiry into "What is life?" and borrowing his title were the ideas of Peter A. Nevraumont. Curiously, all three forgot to provide the original reference. It is: "What is life? The physical aspects of the living cell." Erwin Schrūdinger; Cambridge (England): Cambridge University Press; 1944, 92 p., [based on lectures, Institute of Trinty College, Dublin, February 1943].

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Updated 7 February 2001.




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