What is Life? (review)

What Is Life? by Lynn Margulis and Dorian Sagan. University of California Press, Berkeley and Los Angeles, CA, U.S.A., 2000. 320 pp., illus. $35.00, paper. ISBN: 0-520-22021-8.

Dr. Lynn Margulis is well recognized among scientists 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. Dorian 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 and Schuster 5 years ago.

The book has nine chapters in all, with catchy titles such as "Once upon a Planet" and "Flesh of the Earth." The essence of the senior author's major contribution to the primary literature on symbiogenesis is covered in chapter five, "Permanent Mergers." Chapter three, "Lost Souls," 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." Lovelock 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 and 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.

The 31 color plates in the middle of the book are all of inherent interest, well chosen and nicely reproduced on quality paper; they could 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 black-and-white illustrations and two tables are useful, including schematics of the natural histories of various species. The glossary is new to this edition; 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?", following with a series of summary statements. They acknowledge that the revival of Schrödinger's inquiry into "What is life?" and borrowing his title were the ideas of Peter A. Nevraumont. Curiously, however, all three forgot to provide the original reference, which is: What is Life? The Physical Aspects of the Living Cell, by Erwin Schrödinger (Cambridge Univ. Press: Cambridge, U.K., 1944 [based on lectures, Institute of Trinity College, Dublin, February 1943]). Accordingly, the final statement, in the epilogue, is a bit anticlimactic: "We can ask with curiosity but can answer only tentatively...