One could state as a hypothesis that earthworms cannot survive or do not have natural means of transport across bodies of salt water. This is testable, although it would be difficult to release test worms or cocoons by all possible means of conveyance (rafting vegetation, logs, on debris in violent cyclonic storms and so on), and even harder to track their fates.
—SAMUEL JAMES, Earthworm Ecology, 1998
DARWIN FACED A PARTICULARLY vexing problem during the development of his theory of evolution. He argued that a species can change to adapt to its environment, which is why variations among species could be found in different parts of the world. There were notable differences among the finches he encountered in the Galapagos Islands during his Beagle voyage in 1835, for instance. The popular thinking of the day, however, was that each species was God’s creation, pure and simple. The fact that near-identical animals could be found on far-flung continents around the world only supported this notion. After all, if a species was supposed to change in response to its environment, how could the same flower, insect, or fossil be found in Australia and South America? Surely only divine creation could explain it.
Spiritual matters were often at the heart of Darwin’s internal conflicts about his work. He took great risks by challenging the notion of creationism as it was understood at the time. Scientists like Galileo and Newton, exploring the laws of motion before Darwin’s birth, had made a case that there were, in fact, physical laws that governed the movement of the planets and the stars, as well as the velocity of hail falling from the sky or the speed of a pendulum’s swing. These notions were made more palatable by the belief that God, if not directly responsible for moving heavenly bodies through space, at least created the physical laws governing their movement. God, people could believe, invented the laws of physics, then put them to work. He placed the planets in their orbits, and sent them spinning through space with a puff of heavenly breath.
Darwin struggled with a similar notion. Perhaps God did not intervene directly in the formation of each new creature, or each variation within a species. Perhaps God created the laws of evolution and put them to work on Earth. These questions were no small matter to Darwin. A great deal was at stake. His wife, Emma, was a deeply devout woman and he could not bear the thought of causing her—and her family, the Wedgwoods, with whom the Darwins had many family ties—the shame and public ridicule that his ideas could bring all of them. In fact, for a while he considered hiding his essay on evolution that would eventually become On the Origin of Species and even planned to leave instructions for it to be published after his death. It was not until other scientists began to reach similar conclusions that he felt his work on evolution could be published without bringing ruin on his family.
Still, for years Darwin tried to come up with an explanation—apart from that of divine creation—for the similarities between species on separate continents. Eventually he settled on the notion that identical species could travel to another continent on their own by wind or water. He set out to prove that seeds could be transported across the ocean by soaking them in salt water and germinating them afterwards. When his experiments showed that they would sink in salt water and might not float across the Atlantic as he had originally thought, he moved on to birds. He fed them seeds, then killed and dissected them to retrieve the seeds from their guts and germinate them. He even asked his colleagues for specimens of bird feet caked in mud to demonstrate that seeds could travel across the ocean in this way, and half-rotted bird feet did indeed arrive by post for his inspection.
Although some mapmakers and geologists had noticed as early as the seventeenth century that the continents of the world had parallel coastlines that might have been connected at one time, Wegener’s theory of continental drift was not published until 1912, some thirty years after Darwin’s death. Finally it became obvious that the striking similarities in flora and fauna Darwin saw on his voyage were not, as he feared, damning proof against his theory of evolution. Instead, the presence of like species on different continents could be explained by the very notion that had floated around for centuries before: these continents once fit closely together, like pieces of a puzzle. Even earthworm species follow this pattern, telling the story of the movement of the continents in a way that birds and snakes and crickets cannot. Worms, because they live in the earth, are uniquely qualified to document the movements of land masses.
TRACING EARTHWORMS BACK through the earth’s history is not as easy as it might seem. There are enough similarities between worm species around the world to suggest that they were well established before the continents started drifting apart. But a soft-bodied animal like a worm or a jellyfish does not leave much of an imprint in the fossil record. Worms do make their mark in the earth; occasionally a fossil will turn up with holes running through it that look distinctly like burrows. And fossil records indicate that earthworm ancestors—soft-bodied, water-dwelling creatures that could have been similar to leeches or marine worms—lived in the Cambrian period, around five hundred million years ago. But when did worms first establish themselves on land? One thing is certain: before there were earthworms, there was soil.
The sea level oscillated enough during the Carboniferous period, about 350 million years ago, to form limestone, shale, and sandstone in what would later become North America. Coal-forming swamps contributed to the vast deposits of coal in England. As the oceans advanced and receded, one layer of sediment after another was left behind. In this environment, ferns and early trees flourished. Here, geologists presume, in the roots of these primitive plants, earthworms would have found their niche. By this time, animals were laying hard-shelled eggs, early reptiles were living in the forests, and land snails appeared for the first time, as did millipedes, scorpions, and spiders. Life underground was perhaps not so different from what it is today. Springtails and mites lived in the soil, alongside earthworms, as they do now. And even in this modern age, the habitats of earthworms harken back to their watery beginnings: you won’t find a worm in the desert, and you won’t find one under a glacier. They continue to seek damp, cool soil, as they did in their earliest days.
It is difficult to say with absolute certainty how widespread earthworms might have been when, 248 million years ago, the Permian Mass Extinction wiped out many land-dwelling species and all but about five to ten percent of marine life. The causes of extinctions are in general a source of controversy, but glaciers, volcanic eruptions, and the shifting and grinding of land masses are all considered viable theories. This much is clear: the earthworm persevered. No climate change, no geologic upheaval, has managed to threaten its existence.
What came after—the Triassic and Jurassic periods—is perhaps one of the most familiar times in the Earth’s ancient history. Dinosaurs appeared, the first birds took flight, and flowering plants evolved. (Another mass extinction about sixty-five million years ago wiped out the dinosaurs and about three-quarters of all species living on the planet at that time, but once again, earthworms survived.) These mass extinctions were not, however, the most dramatic events in the earthworm’s history. Something else was happening during the age of the dinosaurs. About two hundred million years ago, a fissure started to form between what is now Africa, North America, and South America, and the Pangea supercontinent began to break apart. Earthworms living on those continents today are so much alike that their very similarity confirms that they once lived together on the Pangea land mass.
THE MOVEMENT OF PANGEA, then, held the answer to Darwin’s questions about the similarities of species around the globe. The fossils, plants, and birds that he found on one continent could be closely related to those on another continent. While he had envisioned birds flying across the ocean with seeds embedded in their feet to explain the similarity between species, we now know that it was not the seeds or the birds that traveled so far. The continents themselves have moved, carrying their inhabitants with them.
It is this very issue that has attracted the attention of Sam James, one of the world’s leading earthworm taxonomists. He realized that if he could map the distribution of earthworms around the globe, he could establish their place in the study of continental drift. The connection between earthworm taxonomy and geology has not been, in his opinion, adequately explored.
“Take the worms you’ve got in your California redwood forests, for example,” he told me on the phone one day. “They’re not very well known, but what we do know about them tells us that their closest relatives are in Australia and New Zealand. How did they get there? Did they wander around the Pacific Rim? Some people say they did just that. On the other hand, there are chunks of eastern Australia embedded in British Columbia. California, Oregon, Idaho, Nevada—they’re made up of sutured island areas and ocean floor crust, all pasted together. And it’s still moving, at least in geologic time. Sit there in Eureka long enough, you’ll see southern California drift by eventually. And what about Africa? We were connected to Africa at one point, but we don’t have any worm species in common. Why? Maybe because that area was desert at the time.
“Or look at the worms in the Caribbean. They’re closely related to worms in Fiji. How did that happen? That’s what I want to find out. You see all these papers published about birds of the Caribbean islands, but you know what? Birds can fly away. Worms can’t get across bodies of saltwater by themselves. If you find a native worm in Mexico that’s related to a worm in Australia, the only possible explanation is the movement of land masses. That’s one area where earthworm science is headed next. Land area patterns. The relationship of worms to the movement of the continents.”
Sam realizes that those relationships can be traced only if we can discover how many species of earthworms live on the planet and where they are. But in some ways, the earthworms inhabiting the globe today are almost as elusive as those that lived hundreds of millions of years ago. Most oligochaetologists start out in another field—forest ecology, biology, botany—and discover along the way that earthworms, which play such a vital role in the ecosystem, are not well classified or understood. In Sam’s case, a semester-long project to investigate their role in a particular prairie turned into a career.
“I started out studying grasslands,” he told me. “Big animals. Cows, buffalo. I was doing research on whether a cow’s spit makes grass grow. Things like that.” A few years after he began this work, a herd of bison was going to be reintroduced to the same kind of prairie their ancestors had once inhabited. “I got myself invited along,” he said. “As soon as they released the animals, I ran out to the paddock and collected all the dung I could carry. I was looking at rapid nutrient cycles. You know, the bison eat the grass, turn it into manure, then the earthworms eat the manure, and they help the grass to grow, which the bison then eat. Then I found out that nobody knew what kind of earthworms were living out there. That’s how it all started.”
Sam has been on several worm-hunting trips to the Philippines and was eager to tell me about the dozens of undiscovered specimens he found and brought back with him. “One is deep indigo blue,” he said. “Eighteen inches long and about a thumb’s width in diameter. It’s got big white spots with yellow centers, like fried eggs, all over its back, if you can imagine that. And get this—it crawls on the forest floor, doesn’t burrow in the ground, and its infants live in trees until they’re mature. Amazing.”
He showed me this worm one time. He pulled it out of a jar so I could get a better look. The preservation process had faded it a little—he had to hold up a photograph of the living specimen so I could appreciate the iridescent blue-green sheen of its skin—but it was still remarkable. It was like nothing I’d ever seen or imagined, like something out of a science fiction movie. I didn’t touch it, but I imagined that it had the texture of a pickle, something that was once pliable and alive but had since stiffened in its brine. It looked more like a small snake than a large worm, except that it had segments running in rings down its body instead of scales. Sam explained that the spots on each worm were different, which is unusual for a creature that is generally symmetrical. “If you were to observe these in the wild somehow,” he said, “you could get to know them by their different spot patterns, the way people learn to tell individual whales or birds apart.
“Down in the Philippines, they have all these posters, you know, like ‘Birds of the Philippines,’ ‘Butterflies of the Philippines,’ that sort of thing. Well, we’re making a ‘Worms of the Philippines’ poster. They’ve got a lot of remarkable worms over there. People don’t realize that.”
Sam James is passionate about discovering and naming unusual species. “I’ve got so many new worms here, I could spend years identifying and classifying them. I’m thinking about putting them all on a website. People can get a worm named after them, or you could get one named for your husband for an anniversary present. You know, like they do with stars. What do you think?”
What do I think? It’s brilliant, I tell him. Everyone will want one.
WITH SO MANY undiscovered species, it’s a wonder that more scientists haven’t picked up a shovel and gone digging for them. Who could help but be entranced by the notion of an indigo worm with yellow and white splotches on its back? Yet there are surprisingly few scientists working on earthworm taxonomy. Canadian scientist John Reynolds is one of the few who has spent a lifetime working in this field. The work is incomplete and, as he told me, terribly underfunded.
“Most worm specialists have to work a day job,” he said. Right now he’s in his ninth career, at a Canadian trucking firm. “I’ve also been a silversmith, a research scientist, a professor, a—oh, let’s see—a lawyer, a police officer, a college dean, a consultant, then I was a truck driver, and now I’m in what you’d call transportation logistics. That means I’m in management here at the trucking company.”
Since 1968, he’s also edited a scientific worm journal called Megadrilogica. I keep a stack of back issues on my desk, next to a pot of earth that sometimes contains a worm I’ve brought in from the garden for a short stay. Each issue of the journal is printed on eleven-by-seventeen-inch paper that, when folded in half and stapled, makes for a neat letter-sized journal that is comforting in the absolute black-and-white certainty with which it elucidates its slippery and evasive subject. There are no illustrations, only a few maps and tables, and long lists of academic citations in the back of each issue. The articles have titles like “Bacteriology of Laying Hen’s Manure, Composting, and Eisenia Foetida (Oligochaeta: Lumbricidae),” “Note on an Indian Earthworm With Two Tails,” and the wistful “Farewell to North American Megadriles.” Reynolds’s own articles tend to have straightforward titles like “The Earthworms of New Brunswick,” “The Earthworms of South Carolina,” and “Primeros Datos de Lombrices de Tierra (Oligochaeta) de la Isla de San Andrés, Colombia” (roughly translated: “The Earthworms of San Andrés Island, Colombia”).
In spite of—or perhaps because of—his various careers, Reynolds has always found a way to get out and collect worms. Lately he’s discovered that truck driving and family vacations provide the best opportunities. “When I was driving a truck, I could pull into any rest stop, turn over a log, and find some worms. Now I’m in management, but some of the truckers pick up worms for me. I send them out with specimen collection kits and they stop off at rest stops and gather worms for my research.
“And this year we’re off to Panama for vacation. I can get the best worms at tourist resorts. They bring in all these plants from the jungle to plant around the hotel, and there’s always worms in the roots. That’s the global distribution of earthworms for you, right there in those ball and burlap bags. I just go around and talk to all the gardeners and get them to bring worms to me. They’ll tell me where they found them, what plants were growing nearby, everything.”
John Reynolds has traveled around the world, gathering and classifying specimens. His collection of one hundred thousand earthworms recently went to the Canadian Museum of Nature. The collection had simply grown too large to curate properly, he told me, and it was something of a relief to let it go to an institution that could make better use of it.
More than any other earthworm scientist I’ve met, Reynolds laments the lack of popular support for worm research. He once wrote, “I have long advocated the necessity for our scientific information to be more accessible to the general non-scientific community. We are a small group of scientists working with limited finances and materials. We have suffered from not following the examples of entomologists and ornithologists. These disciplines have advanced more rapidly because of the contributions of ‘amateurs’ and general collectors.” Still, he faces an uphill battle in his quest to rally the public around the cause of earthworm science and preservation. “I do radio, television, public lectures. People ask me, why bother cataloging earthworms? Well, why catalog anything? It’s how we learn about the world we live in. Besides, some of these worms are going extinct. How do you know what you’re losing if you don’t know what you have?”
ONCE AN EARTHWORM is discovered, it has to be classified and named. Worms are grouped under the same branch of the animal kingdom’s family tree, phylum Annelida, as leeches and aquatic worms, pointing to their early connection with water-dwelling organisms five hundred million years ago.
Within the phylum Annelida, earthworms are organized under the class Oligochaeta, and beyond that, taxonomists disagree. Recent classifications have identified two orders, several suborders and superfamilies, 23 families, 739 genera, and over 4,500 species. Here is an example of earthworm taxonomy for Lumbricus terrestris, which was identified by Linnaeus in 1758 (and was the only one he described):
Kingdom: Animalia
Phylum: Annelida
Class: Oligochaeta
Order: Haplotaxida
Family: Lumbricidae
Genus: Lumbricus
Species: Terrestris
The constant shifting and reclassifying of earthworms is frustrating to all but the most dedicated taxonomist. When I complained to Sam James about all the contradictions in the literature, he said in a matter-of-fact voice, “This is routine with emerging science. We’re fixing mistakes. In the next century, we’ll start to see the complete family tree.”
Oligochaetologists today are studying questions that, for many insects and animals, were answered in the last century. That’s not to say that a great deal of progress has not been made: since Darwin’s day, scientists have managed to quantify the extent to which earthworms not only plough the earth, but transform the organic life of the soil. But it could be years before the complex relationships between plants and soil-dwelling creatures are fully understood. Meanwhile, taxonomists like Sam James are still identifying and describing new species. When I saw the wooden case in Sam’s laboratory filled with vials of preserved worms, each shelf in the case marked by the country in which the worm was found, I told him that his collection more closely resembled that of a nineteenth-century naturalist than that of a twenty-first-century researcher.
“This is the sort of collection that I picture the young Darwin putting together in the 1830s after his trip around the world on the Beagle,” I said. “It looks so old-fashioned. How many scientists today get to fill their labs with new species like this?”
“Not many,” he said. “You’re right. In some ways, we are back in the nineteenth century.”
IT MUST BE BOTH a joy and a frustration to work on the frontiers of science. Sam James, like most of the oligochaetologists I met, is a passionate advocate for the subjects he studies, genuinely unable to understand why everyone isn’t as fascinated as he is with earthworms. It is reasonable for such a person to look at the many societies established for the study and appreciation of birds or butterflies or at the laws in place to protect dolphins and starfish, and the lengths to which people will go to attract ladybugs or honeybees to their gardens, and wonder why no comparable efforts have been made on behalf of earthworms. Are we so hierarchical that we can’t respect a creature that lives beneath our feet? Are we so focused on image, on appearance, that we can only love the prettiest inhabitants of the garden—a swallowtail butterfly, a fat bumblebee—and neglect the slimy but hardworking earthworm? Perhaps it is because we associate them with death and decay, while bees bring to mind sunflowers and sweet honey and the mild sexual buzz of a flower bed being pollinated.
Still, earthworm scientists work on, alone, undeterred by the lack of popular support. Their discoveries—the unusual and extraordinary worms they collect—might someday be stored at the Smithsonian or the American Museum of Natural History, but they may not be exhibited for years. You can get a map that shows the distribution of red fire ants across the southern United States, one that shows where redwood forests used to grow worldwide and where they remain today, even a map showing the location of the endangered Oahu tree snail. But you can’t get a reliable map of the distribution of earthworm species worldwide, precisely because worms live underground and must be dug up, one at a time, in order to be identified and counted. Once they’ve been discovered, it could be months or years before a researcher has time to properly name and catalog the species.
I once asked Sam if he knew anything about earthworms in the Amazon basin. He said he could think of a few, including some giant worms over two feet long. When I asked him for a Latin name, he said, “I don’t know. I haven’t named them yet.” If he doesn’t name them, I wondered, who will?