1
PROTOZOA
Down the Steps
You walk ten steps down on a stairway shaped from breakwater rocks straight into the water, which is flat and still, right at the top of the tide. Sound recedes with gravity and light fades to soft green as you dip beneath the surface. All you can hear is your breathing.
Soon you are in a sponge garden, in a jumble of shapes and colors. Some of the sponges have the form of bulbs or fans, growing upward from the seafloor. Others spread sideways over whatever they find, in an irregular encompassing layer. Amid the sponges are what look like ferns and flowers, and also ascidians (with a silent “c”), pale pink spout-like structures with enamel patterns inside. The spouts resemble the downward-curved air funnels on the decks of ships, though these spouts face in every direction. They are covered by all manner of tangled life, often so encrusted that they appear to be part of the physical landscape in which things live rather than organisms in their own right.
But the ascidians make small shifts, as if asleep and half sensing you as you pass. Occasionally, and always startling me a little, an ascidian body half-collapses in place and visibly expels the water held inside the animal, as if with a shrug and sigh. The landscape comes to life and makes its own comment as you go by.
Among the ascidians are anemones and soft corals. Some corals take the form of a cluster of tiny hands. Each hand has the regularity of a flower, but a flower that grasps at the water around it. They clench and slowly open again.
You are swimming through something like a forest, surrounded by life. But in a forest, most of what you encounter is the product of a different evolutionary path: the plant path. In the sponge garden, most of what you see are animals. Most of those animals (all except the sponges themselves) have nervous systems, electrified threads that stretch through the body. These bodies shift and sneeze, reach and hesitate. Some react abruptly as you arrive. Serpulid worms look like tufts of orange feather fixed to the reef, but the feathers are lined with eyes, and they vanish if you come too close. One can imagine being in a green forest, and finding the trees sneezing and coughing, reaching out hands, glimpsing you with invisible eyes.
This slow swim out from shore is showing you remnants and relatives of early forms of animal action. You are not swimming into the past—the sponge, ascidian, and coral are all present-day animals, products of the same span of evolutionary time that produced humans. You are not among ancestors but far-removed cousins, distant living kin. The garden around you is made of the topmost branches of a single family tree.
Farther out and under a ledge is a tangle of feelers and claws: a banded shrimp. Its body, partly transparent, is just a few inches long, but antennae and other appendages extend its presence at least three times as far. This animal is the first I’ve mentioned that might see you as an object, rather than responding to washes of light and looming masses. Then a bit farther still, on top of the reef, an octopus is stretched out like a cat—a very camouflaged cat—with several arms extended and others curled. This animal watches you, too, more overtly than the shrimp, raising its head in attention as you pass.
Matter, Life, and Mind
Something was dredged from the depths of the North Atlantic by HMS Cyclops in 1857. The sample looked like seafloor mud. It was preserved in alcohol and sent to the biologist T. H. Huxley.*
The sample was sent to Huxley not because it seemed especially unusual, but because of an interest, both scientific and practical, in seafloors at the time. The practical interest stemmed from the project of laying deep-sea telegraph cables. The first cable to span and send a message across the Atlantic was completed in 1858, though it lasted only three weeks, when the insulation failed and the signal-carrying current leaked away into the sea.
Huxley looked at the mud, noted some single-celled organisms and puzzling round bodies, and stored the sample away for about ten years.
He returned to it then with a better microscope. This time he saw discs and spheres of unknown origin, and also a slime-like substance, a “transparent gelatinous matter,” surrounding them. Huxley suggested that he had found a new kind of organism, of an exceptionally simple form. His cautious interpretation was that the discs and spheres were hard parts produced by the jelly-like matter itself, which was alive. Huxley named the new organism after Ernst Haeckel, a German biologist, illustrator, and philosopher. The new form of life was to be called Bathybius Haeckelii.
Haeckel was delighted with both the discovery and christening. He had been arguing that something like this must exist. Haeckel, like Huxley, was entirely convinced by Darwin’s theory of evolution, unveiled in On the Origin of Species in 1859. Huxley and Haeckel were the leading advocates of Darwinism in their respective countries, England and Germany. Both were also eager to press on to questions that Darwin had been reluctant, beyond a few brief passages, to speculate about: the origin of life and the beginning of the evolutionary process. Did life arise just once on Earth, or several times? Haeckel was convinced that the spontaneous generation of life from inanimate materials was possible, and might be going on continually. He embraced Bathybius as a fundamental form of life, one that might cover large tracts of the deep seafloor; he saw it as a bridge or link between the realm of life and the realm of dead, inorganic matter.
The traditional conception of how life is organized, a picture in place since the ancient Greeks, recognized just two kinds of living things: animals and plants. Everything alive had to fall on one side or the other. When the Swedish botanist Carl Linnaeus devised a new scheme of classification in the eighteenth century, he installed plant and animal kingdoms alongside a third, inanimate realm, the “kingdom of rocks,” or Lapides. This three-way distinction is still seen in the familiar question, “animal, vegetable, or mineral?”
By the time of Linnaeus, microscopic organisms had been observed, perhaps first in the 1670s by the Dutch draper Antonie van Leeuwenhoek, who made the most powerful of the early microscopes. Linnaeus included a fair number of tiny, microscopically observed organisms in his classification of beings, putting them in the category of “worms.” (He concluded the tenth edition of his Systema Naturae, the edition that began the classification of animals as well as plants, with a group he called Monas: “body a mere point.”)
As biology progressed, puzzle cases began to appear, especially at the microscopic scale. The tendency was to try to put them with either plants (algae) or animals (protozoa), on one side of the boundary or the other. But it was often hard to tell where some new creature belonged, and natural to feel that the standard classification was under strain.
In 1860, the British naturalist John Hogg argued that the sensible thing to do was to cease the shoehorning and add a fourth kingdom for the small organisms, increasingly recognized as single-celled, that are neither plants nor animals. These he called Protoctista, and he placed them in a Regnum Primigenum, or “primeval kingdom,” that accompanied animals, plants, and minerals. (Hogg’s term, Protoctista, was later shortened by Haeckel to the more modern Protista.) As Hogg saw it, the boundaries between the different living realms were vague, but the boundary between the mineral kingdom and the living was sharp.
The wrangling of categories I’ve described has so far been concerned with life, not with the mind. But life and the mind have long seemed linked somehow, even if their perceived relationship has not been stable. In the framework of Aristotle, developed over two millennia earlier, soul unifies the living and the mental. Soul, for Aristotle, is a kind of inner form that directs bodily activities, and it exists in different levels or grades in different living things. Plants take in nutrients to keep themselves alive—that shows a kind of soul. Animals do this and can also sense their surroundings and respond—that is another kind of soul. Humans can reason, in addition to the other two capacities, and so have a third kind. For Aristotle, even inanimate objects that lack souls also often behave in accordance with purposes or goals, tending toward their natural place.
Copyright © 2020 by Peter Godfrey-Smith
“Wodwo” from Collected Poems by Ted Hughes. Copyright © 2003 by the Estate of Ted Hughes. Reprinted by permission of Farrar, Straus and Giroux.