It bears remembering that we spend our lives trying to discern where we end and the rest of the world begins. The puzzlement is so immense precisely because the boundary between us and not-us is profoundly permeable — we become ourselves through communion and conviviality with what is not us. This is as true existentially as it is evolutionarily, for symbiosis — not competition — is the mightiest propulsive force of evolution.
To this truth the visionary evolutionary biologist Lynn Margulis (March 5, 1938–November 22, 2011) devoted her life, crystalized in her influential Gaia hypothesis — the notion that organisms interact with their environment to make of Earth a synergistic, self-regulating crucible of life.
Living beings defy neat definition. They fight, they feed, they dance, they mate, they die. At the base of the creativity of all large familiar forms of life, symbiosis generates novelty. It brings together different life-forms, always for a reason. Often, hunger unites the predator with the prey or the mouth with the photosynthetic bacterium or algal victim. Symbiogenesis brings together unlike individuals to make large, more complex entities. Symbiogenetic life-forms are even more unlike than their unlikely “parents.” “Individuals” permanently merge and regulate their reproduction. They generate new populations that become multiunit symbiotic new individuals. These become “new individuals” at larger, more inclusive levels of integration. Symbiosis is not a marginal or rare phenomenon. It is natural and common. We abide in a symbiotic world.
Properly understood, the biology of symbiosis undermines our most tightly held intuitions about the nature of the self as a distinct entity separate from other selves — an illusory separation dissolved in the biological reality of all living beings, but rendered most clearly visible in some of the simplest. A generation after Lewis Thomas wrote so lyrically about the symbiotic life of a jellyfish and a sea slug — which remains the finest thing I have ever read on the paradoxes and mysteries of the self — Margulis details another living antidote to what Pablo Neruda rightly indicted as our illusion of separateness:
In Brittany, on the northwest coast of France, and along beaches bordering the English Channel is found a strange sort of “seaweed” that is not seaweed at all. From a distance it is a bright green patch on the sand. The patches slosh around, shimmering in shallow puddles. When you pick up the green water and let it slip through your fingers you notice gooey ribbons much like seaweed. A small hand lens or low-power microscope reveals that what looked like seaweed are really green worms. These masses of sunbathing green worms, unlike any seaweed, burrow into the sand and effectively disappear. They were first described in the 1920s by an Englishman, J. Keeble, who spent his summers at Roscoff. Keeble called them “plant-animals” and diagrammed them splendidly in the color frontispiece of his book, Plant-Animals. The flatworms of the species Convoluta roscoffensis are all green because their tissues are packed with Platymonas cells; as the worms are translucent, the green color of Platymonas, photosynthesizing algae, shows through. Although lovely, the green algae are not merely decorative: they live and grow, die and reproduce, inside the bodies of the worms. Indeed they produce the food that the worms “eat.” The mouths of the worms become superfluous and do not function after the worm larvae hatch. Sunlight reaches the algae inside their mobile greenhouses and allows them to grow and feed themselves as they leak photosynthetic products and feed their hosts from the inside. The symbiotic algae even do the worm a waste management favor: they recycle the worm’s uric acid waste into nutrients for themselves. Algae and worm make a miniature ecosystem swimming in the sun. Indeed, these two beings are so intimate that it is difficult, without very high-power microscopy, to say where the animal ends and the algae begin.
The living world, Margulis observes, is rife with such symbiotic bonds that challenge the notion of where one self ends and another begins. There is the Plachobranchus snail, inside which is an inner garden of green symbionts so perfectly arranged in neat rows that they appear planted by an invisible hand; there is the Mastigias jellyfish with its tiny green umbrellas animated by single-celled zooxanthellae; there is the giant clam, Tridacna gigas, which orients ints entire colossal body toward the light for the benefit of the greenhouse of algae living inside it.
Then there are, of course, we — we who contain multitudes, our microbiome living as a portable universe within us. “Masses are rude, lame, unmade, pernicious in their demands and influence,” Emerson inveighed. “I wish… to tame, drill, divide, and break them up, and draw individuals out of them.” But the patron saint of self-reliance was tragically antiscientific in his philosophy — in the living world, individuals as such simply don’t exist. There are only masses, some of whom move about with the illusion of individuality. Margulis writes:
We animals, all thirty million species of us, emanate from the microcosm. The microbial world, the source and well-spring of soil and air, informs our own survival. A major theme of the microbial drama is the emergence of individuality from the community interactions of once-independent actors.
With an eye to our evolutionary future, itself a vista of tremendous humility, she adds:
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.
Complement with Iris Murdoch on how art unselves us and Helen Macdonald on the total solar eclipse as an instrument of unselfing, then revisit Margulis on the interconnectedness of life across time, space, and species.