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Thursday, June 12, 2008

Book Review: Symbiotic Planet

Symbiotic Planet: A New Look At Evolution, by Lynn Margulis. Basic Books, 1998.

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"Animal, vegetable, or mineral?" So opens every round of Twenty Questions, with a query intended as the base classification for anything on earth.

But is it really so simple? Lynn Margulis begins her book Symbiotic Planet with a challenge to our received notions about the forms of life on earth. Introducing us to "a strange sort of 'seaweed' that is not seaweed at all," she describes a green organism found in tidepools along the coast of Brittany in northwest France. Superficially similar to green stringy seaweed, these verdant threads are in fact thin transparent worms, inside whose bodies photosynthetic algae grow. The worms luxuriate on the surface of warm shallow tidepools, allowing their internal algae to soak up the sun, synthesize sugars, and deliver the worm hosts a nourishing meal intravenously, as it were. In turn, the algae benefit from the worms' motility, which takes them to the sunniest spots to photosynthesize, or buries them in the sand to hide from predators. Waste products from the worms' digestion become nutrients for the algaes' growth.

Animal, or vegetable? In a symbiotic relationship such as this, the answer is not clear-cut. Frederick William Keeble, the discoverer of the seaweed-worms, compromised in his 1920's treatise by dubbing them "plant-animals." Furthermore, the case of Convoluta roscoffensis, as the seaweed-worms are scientifically known, is anything but anomolous. In Symbiotic Planet, Margulis gives us example after example of symbiotic partnerships between jellyfish and algae, between cows and protists, all defying the rigid boundaries we normally take for granted to divide kingdoms of life.

A simple hand-lens suffices to detect the symbiotic green algae inside their transparent worm hosts. Turn to a scanning electron microscope to probe the internal workings of an animal cell as it digests sugar. Inside the cell are mitochondria, oxidizing the sugar to release energy stored in its chemical bonds. These mitochondria, though so integrally incorporated in an animal's cells, so deeply implicated in its very sustenance, have an independent ancestry as free-living, oxygen-breathing bacteria. Over generations their symbiosis with host cells became so routinized that neither symbiont could survive without the other, and the oxygen-breathing bacteria renounced their individuality to become mitochondria, organelles inside cells. Mitochondria still carry their own bacterial DNA, resembling that of modern-day independent oxygen-breathing bacteria.

Symbiotic Planet is, first and foremost, a book about innovation. Describing the incorporation of free-living bacteria as mitochondria and other cell organelles, 'serial endosymbiosis theory' is Margulis's prime scientific innovation, and the story of this theory's development forms a major thread in the narrative. Part scientific memoir, Symbiotic Planet chronicles Margulis's brilliant and unorthadox career, as well as her ideological influences ranging from such luminaries as Gregor Mendel to the obscure but prescient Konstantin Merezhkovsky (1855-1921). A Russian botanist specializing in the study of lichens, Merezhkovsky rejected Darwinism as failing to provide a complete explanation for the development of new species through natural selection.

Konstantin Merezhkovsky

According to Merezhkovsky and Margulis, it is not natural selection but symbiosis which truly advances evolutionary innovation. Natural selection can hone the adaptation of a species to its niche, but Darwin's Origin of Species fails to live up to its title in that it does not describe the origin of any new species at all, but merely the development of existing species under selection pressures. The overlooked importance of symbiosis in combining disparate life-forms to create a new whole would have been clear to Merezhkovsky through his study of lichens, which are in fact a symbiotic pairing of algae and fungi.

Haeckel, Lichenes. 1904.

Symbiotic Planet paints for us a new picture of nature. While the eat-or-be-eaten, survival-of-the-fittest model familiar from introductory accounts of Darwinism appropriately describes inter- and intra-species competition driving natural selection, there is more to the story. The symbiotic incorporation of bacteria as mitochondria took place over the course of a "violent, competitive, and truce-forming past," writes Margulis. Having tried and failed to eat another bacterium, some primal cell must have made the decision to keep its undigested and still-living dinner as a functioning member of its own expanded body. This creative merger represented an evolutionary jump unachievable by simple random genetic variation.

Our neglect of symbiosis is not confined to an academic debate on the nature of evolution. Not only do we reconstruct from the fossil record an imagined history in which symbiosis plays but a minor role, we envisage our own future on the planet as an extension of the simplistic survival-of-the-fittest paradigm. Margulis whimsically describes her bemusement on watching an episode of Star Trek for the first time:

"I was struck by its silliness. The lack of plants, the machinate landscape, and in the starship, the absence of all nonhuman life-forms seemed bizarre. Humans, if someday they trek in giant spaceships to other planets, will not be alone. In space as on Earth, the elements of life, carbon, oxygen, hydrogen, nitrogen, sulfur, and phosphorus and a few others, must recycle. This recycling is no suburban luxury; it is a principle of life from which no technology can deliver us. Human voyages into deep space require ecosystems composed of many nonhuman organisms to recycle waste into food. Only very short stints in constant contact with mother Earth are possible in the absence of 'ecosystem services.'"

Although hypothetical future intergalactic adventure may seem like a frivolous example, the human-centric character of these imagined odysseys is telling. Such narrowness of focus has brought on the crisis of dwindling nonrenewable resources, such as peak oil. Bent only on the immediate extension and expedition of our existing technologies, we have used the resources which are readily at hand, however temporarily, and without thought for collateral consequence.

Margulis writes at the end of Symbiotic Planet's opening chapter,

"The tendency of 'independent' life is to bind together and reemerge in a new wholeness at a higher, larger level of organization. I suspect that the near future of Homo sapiens as a species requires our reorientation toward the fusions and mergers of the planetmates that have preceded us in the microcosm."

Rather than using oil to power lawn mowers on municipal grounds, why not move to a symbiotic solution, as Silicon Valley has recently done in employing goats to graze down brush-covered areas? For that oil we have already converted to plastic now littering drains and clogging sewers, perhaps newly-discovered plastic-eating microbes can break it down. Both these solutions are merely preliminary moves toward a more symbiotic mode of innovation.

Symbiotic Planet closes with a chapter on Gaia theory, the study originating from James Lovelock's observation that the Earth's surface behaves like a living system in homeostasis. Although Margulis advances as motivation for Symbiotic Planet the quip "Gaia is just symbiosis as seen from space," the final chapter on Gaia theory is the book's weakest section.

While the rest of the book is bold and original, the chapter on Gaia theory is mainly reactionary, and herein lies its disappointment. Margulis spends a large proportion of the chapter in disclaimers and debunkings of romantic notions nonscientific people might draw from a misunderstanding of Gaia theory's premises. To the mythologically and anti-scientifically inclined, Gaia and the concept of a living Earth may appear to represent a antropomorphized Earth-mother goddess who personally manages the planet's cycles.

Certainly such a picture is a misapprehension of Gaia theory, which though fancifully named is a serious branch of science. Every scientist rankles at undeserved censure from anti-science detractors, but worse is to be mistakenly applauded as a champion of their cause, as Gaia theory sometimes has been. More intriguing to read, however, would be a development of the fascinating ideas Margulis presents in the preceding chapter of Symbiotic Planet, detailing the manner in which symbiosis allowed life to extend its range to dry shores, beyond the nutrient-filled sea where it originated. By gradual collaborations and fusions, life became more and more adapted for carrying its necessary elements to new frontiers. Ever more creative instances of symbiosis went hand in hand with the expansion of ecosystems to cover the whole Earth, resulting in the Gaia phenomenon of a self-regulating, living globe. A symbiotic planet is a homeostatic planet.

Margulis's objections to the popular Earth-goddess myth extend beyond the defense of Gaia theory as legitimate science. Promoting conservation as our responsibility to "heal our sick planet" is, to Margulis, simply another instance of human hubris and inflated self-importance. She writes,

"...[T]he planet is not human, nor does it belong to humans. No human culture, despite its inventiveness, can kill life on this planet, were it even to try. More an enormous collection of interacting ecosystems, the Earth as Gaian regulatory physiology transcends all individual organisms. Humans are not the center of life, nor is any other single species."

A few paragraphs later, discussing the early evolution of blue-green algae (cyanobacteria), Margulis continues,

"Oxygen was expelled as a metabolic waste product. This waste, at first disastrous, eventually powered life's continued growth. New wastes test life's tolerance and stimulate life's creativity. The oxygen we need to breathe began as a toxin; it still is. The oxygen release from millions of cyanobacteria resulted in a holocaust far more profound than any human environmental activity. Pollution is natural."

These passages sound, at first blush, shockingly anti-conservationist. If pollution is natural, should we stop worrying about the emissions from our cars, in the expectation that some carbon monoxide-loving organism will evolve to lap up our exhaust? Should we throw our plastic bottles in the ocean to provide dinner for some future phthalate-lover?

Certainly we could, Margulis opines, destroying not life in the long run but merely ourselves. To quote from Symbiotic Planet's concluding chapters,

"The planet will not permit our populations to continue to expand. Runaway populations of bacteria, locusts, roaches, mice, and grass always collapse. Their own wastes disgust as crowding and severe shortage ensue."
As to the continuation of life after our demise, Margulis writes,
"The notion that we can destroy all life, including bacteria thriving in the water tanks of nuclear power plants or boiling hot vents, is ludicrous. I hear our nonhuman brethren snickering, 'Got along without you before I met you, gonna get along without you now,' they sing about us in harmony."

Reading such passages generates at first an uncomfortable feeling that the environmental movement is being cut down to size as a rather mean and self-serving endeavor. No longer our hope to revitalize our engagement in Earth's ecosystems, it seems, in an existential turn of plot, to be merely our last bet at saving our own miserable skins.

The foregoing chapters of Symbiotic Planet, however, hold in themselves the bright alternative to this dour prospect. "We" are not in fact an isolated or isolable phenomenon. As Margulis beautifully puts it, we are "a kind of baroque edifice," having "guts and eyelashes festooned with bacterial and animal symbionts." We are a product of our "coevolving, pointillist bacterial ancestry." Saving ourselves cannot be a mean or narrow enterprise, because it will require a practical realization of the fact that we are not independent individuals, but emergent phenomena resulting from the cooperation of myriad disparate participants. If we can become conscious symbionts in the future, just as we are unconscious products of past and present symbioses, then all that "we" are and all we touch stands a chance at survival and continued thriving.


  1. Great review. I love hearing about books that (despite the last chapter) offer solutions and shifts in thinking to our current prediment. Thank you for posting this.

  2. Thanks, Green Bean. It was actually quite incredible to read Cradle to Cradle immediately after Symbiotic Planet - I felt that they took a lot of ideas from the natural world such as Margulis discusses, and found ways to apply them in industry. I have a lot more to say about this... :-)

    Thank *you* for initiating the Bookworm challenge!