Born in 1913, American physician and writer Lewis Thomas began accompanying his father, a family physician, on house calls at an early age. He went on to pioneer medical breakthroughs in immunology. The following two excerpts are from The Lives of a Cell: Notes of a Biology Watcher, in which Thomas, drawing from his expertise in cellular biology, observes that the earth operates much like a single living cell. Excerpted from “Natural Man,” copyright © 1973 by the Massachusetts Medical Society, from The Lives of a Cell by Lewis Thomas. Used by permission of Viking Penguin, a division of Penguin Group (U.S.A.) Inc.


We are not the masters of nature we thought ourselves; we are as dependent on the rest of life as are the leaves or midges or fish. We are part of the system. One way to put it is that the earth is a loosely formed, spherical organism, with all its working parts linked in symbiosis. We are, in this view, neither owners nor operators; at best, we might see ourselves as motile tissue specialized for receiving information — perhaps, in the best of all possible worlds, functioning as a nervous system for the whole being.

There is, for some, too much dependency in this view, and they prefer to see us as a separate, qualitatively different, special species, unlike any other form of life, despite the sharing around of genes, enzymes, and organelles. No matter. There is still the underlying idea that we cannot have a life of our own without concern for the ecosystem in which we live, whether in majesty or not. This idea has been strong enough to launch the new movements for the sustenance of wilderness, the protection of wildlife, the turning off of insatiable technologies, the preservation of “whole earth.”

The truth is, we have become more deeply involved than we ever dreamed. The fact that we sit around as we do, worrying seriously about how best to preserve the life of the earth, is itself the sharpest measure of our involvement. It is not human arrogance that has taken us in this direction, but the most natural of natural events. We developed this way, we grew this way, we are this kind of species.

We have become, in a painful, unwished-for way, nature itself. We have grown into everywhere, spreading like a new growth over the entire surface, touching and affecting every other kind of life, incorporating ourselves. The earth risks being eutrophied by us. We are now the dominant feature of our own environment. Humans, large terrestrial metazoans, fired by energy from microbial symbionts lodged in their cells, instructed by tapes of nucleic acid stretching back to the earliest live membranes, informed by neurons essentially the same as all the other neurons on earth, sharing structures with mastodons and lichens, living off the sun, are now in charge, running the place, for better or worse.

Or is it really this way? It could be, you know, just the other way around. Perhaps we are the invaded ones, the subjugated, used.

Certain animals in the sea live by becoming part-animal, part-plant. They engulf algae, which then establish themselves as complex plant tissues, essential for the life of the whole company. I suppose the giant clam, if he had more of a mind, would have moments of dismay on seeing what he has done to the plant world, incorporating so much of it, enslaving green cells, living off the photosynthesis. But the plant cells would take a different view of it, having captured the clam on the most satisfactory of terms, including the small lenses in his tissues that focus sunlight for their benefit; perhaps algae have bad moments about what they may collectively be doing to the world of clams.

With luck, our own situation might be similar, on a larger scale. This might turn out to be a special phase in the morphogenesis of the earth when it is necessary to have something like us, for a time anyway, to fetch and carry energy, look after new symbiotic arrangements, store up information for some future season, do a certain amount of ornamenting, maybe even carry seeds around the solar system. That kind of thing. Handyman for the earth.

I would much prefer this useful role, if I had any say, to the essentially unearthly creature we seem otherwise on the way to becoming. It would mean making some quite fundamental changes in our attitudes toward each other, if we were really to think of ourselves as indispensable elements of nature. We would surely become the environments to worry about the most. We would discover, in ourselves, the sources of wonderment and delight that we have discerned in all other manifestations of nature. Who knows, we might even acknowledge the fragility and vulnerability that always accompany high specialization in biology, and movements might start up for the protection of ourselves as a valuable, endangered species. We couldn’t lose.