The Book of Eels

by Patrik Svensson

  I reeled it in as slowly as I could, without letting the line slacken, as though savoring the moment. But it was a short line, and there were no reeds for this eel to hide in; before long, I pulled it out of the water and saw its shiny yellowish-brown body twisting in the early-morning light. I tried to grab it behind its head, but it was virtually impossible to hold. It wrapped itself around my arm like a snake, up past my elbow; I could feel its strength like a static force more than movement. If I dropped it now, it would escape through the grass and back into the water before I could get a secure hold.

  In the end, we got the hook out and Dad filled the bucket with water from the stream. I slipped the eel in, and it immediately started swimming around and around the inside; Dad put his hand on my shoulder, said it was a beauty. We moved on to the next spiller, stepping lightly up the bank. And I got to carry the bucket.

  3

  Aristotle and the Eel Born of Mud

  There are circumstances that force us to choose what to believe. The eel is one such circumstance. If we choose to believe Aristotle, all eels are born out of mud. They simply appear, as though out of thin air, in the sediments at the bottom of the sea. In other words, they’re not created by other eels reproducing, by the union of reproductive organs and the fertilization of an egg.

  Most fish, Aristotle wrote in the fourth century BCE, do, of course, lay eggs and breed. But the eel, he explained, is an exception. It is neither female nor male. It neither lays eggs nor mates. Eels do not give life to other eels. The spark of their life comes from somewhere else.

  Aristotle suggested: Study a small pond with a tributary during a period of drought. When the water has evaporated and all the mud and muck has dried out, there is no life at all to be found on its hardened bottom. No life can be sustained there, much less a fish. But when the first rain comes and the water slowly returns, something incredible happens. Suddenly, the pond is once more full of eels. Suddenly, they’re just there. The rainwater brings them into existence.

  Aristotle’s conclusion was that eels simply spring into being, like a slithering, enigmatic miracle.

  Aristotle’s interest in eels is not entirely unexpected. He was interested in all forms of life. He was, of course, a thinker and theoretician and the man who, along with Plato, laid the foundation for all Western philosophy; but more than that, he was a scientist, at least by the standards of his age. It’s often said that Aristotle was the last person to “know it all”; or in other words, he was the last person to possess all the knowledge accumulated by humanity. And, among other things, he was ahead of his time when it came to observing and describing nature. His great work Historia Animalium (The History of Animals) was a first attempt, more than two thousand years before Linnaeus, to systematically categorize the animal kingdom. Aristotle observed and described a wide range of animals and what differentiated one from another. What they looked like, their body parts, coloring, and shape, how they lived and procreated, what they ate, their behaviors. Modern zoology grew out of the Historia Animalium; it remained a standard work in the natural sciences well into at least the seventeenth century.

  Aristotle grew up in Stagira on Chalcidice: a peninsula ending in three narrow spits of land that jut out into the Aegean Sea, like a hand with three fingers. His life was one of privilege, with a father who was physician to the Macedonian king; he received a good education, and his father likely envisioned a future as a doctor for his son. But Aristotle was orphaned at a young age. His father died when he was about ten, his mother probably before that. He was taken in by a relative and at seventeen was sent to Athens to study at the finest school in antiquity, the Platonic Academy. A young man, alone in a strange city, curious and brilliant and with a passion for understanding the world that can be comprehended only by those whose own roots have been severed. He studied at Plato’s feet in Athens for twenty years and in many respects came to be his equal. When Plato died and Aristotle was not appointed the new head of the Academy, he relocated to the island of Lesbos. It was there that he began to study animals and nature in earnest. Perhaps that was also where he first started thinking about how eels came to be.

  Not much is known about Aristotle’s scientific method. He didn’t keep notes on his observations and dissections. He gave confident and detailed accounts of his discoveries and insights, but rarely said anything about how he had come to them. Nevertheless, we can be almost entirely certain that he personally performed many of the dissections that form the basis of Historia Animalium. Crucially, it seems clear he spent much of his time studying aquatic life-forms, and primarily the eel. If nothing else, his writings on what is hidden inside the eel, about the relative placement of its organs and the construction of its gills, are particularly copious and detailed.

  Where the eel is concerned, he also often disagreed with other scientists whose names have been lost to posterity, as though the eel was already, at that time, a source of speculation, contradictory opinions, and conflict. Aristotle insisted categorically that eels never carry eggs in their bodies, declaring that anyone who claimed otherwise simply had not studied eels closely enough. There can be no doubt this is so, he wrote, because when you cut open an eel, not only will you not find eggs, you will also not find any organs for producing or transporting eggs or milt. Nothing about the eel’s existence explains how it is brought to life. He also stated that anyone claiming the eel gives birth to live young had been misled by his ignorance and that his opinions were not based on fact. Aristotle also made short shrift of those scientists who claimed eels could be sexed, pointing to the male head as being larger than that of the female. They had simply mistaken interspecies variation for sexual variation.

  Aristotle had studied eels, that much is clear. Maybe on Lesbos, maybe in Athens. He had dissected them and studied their internal organs, had looked for eggs and reproductive organs and an explanation as to how they procreate. He had probably handled a great many eels, scrutinizing them, pondering what kind of creatures they were. And he had reached the conclusion that the eel is a thing unto itself.

  The approach to understanding animals and nature developed by Aristotle would eventually come to shape—virtually single-handedly—both modern biology and the natural sciences, and thus all subsequent attempts to understand the eel. It was above all empirical. Nature can be described through systematic observation, Aristotle claimed, and only through correct description can it be understood.

  It was a radical approach and, in every respect, a successful one. Many of Aristotle’s observations were surprisingly precise, not least considering they were made long before the field of zoology even existed as a concept. His knowledge was way ahead of his time, particularly when it came to aquatic species. He explained and described, for example, the anatomy and reproduction of octopuses in a way that modern zoology was able to verify only in the nineteenth century. And with regards to the eel, Aristotle claimed, correctly, that it can move between freshwater and saltwater, that it has unusually small gills, and that it is nocturnal, hiding in deeper water during the day.

  But the eel was also a subject about which Aristotle made an unusual number of obviously outlandish claims. Despite his systematic method based on observation, he never did manage to understand the eel. He wrote that eels eat grass and roots and sometimes even mud. He wrote that it has no scales. He wrote that it lives for seven or eight years and that it can survive for five or six days on land and even longer if the wind blows from the north. And, as already mentioned, he asserted that eels do not have biological sex and that they are created from nothing. The first embodiment of the eel, Aristotle concluded, is in fact a small maggot-like creature, a kind of earthworm that is spontaneously and without the involvement of any other living thing generated from mud. This worm can spring to life in both seas and rivers, especially where there is plenty of decomposing vegetation, and it prefers shallow marshes or beds of seaweed where the sun warms the water. “There can be no doubt about this being so,” Aristotle wri
tes, and then wraps up his discussion. “Enough about the reproduction of the eel.”

  ALL KNOWLEDGE COMES FROM EXPERIENCE. THAT WAS ARISTOTLE’S first and most fundamental insight. Any study of life must be empirical and systematic. Reality must be described as it is perceived by our senses. First, one establishes that something is; then one can focus on the question of what it is. And only when one has collected all the facts about what something is, is it possible to approach the metaphysical question of why it is the way it is. That is also the insight that has served as the basis for most attempts to gain a scientific understanding of the world since Aristotle’s time.

  But why is it that the eel was able to slither out of Aristotle’s grasp? That is the question that seems impossible to answer. No matter how meticulously and systematically he studied the eel, he reached conclusions that now appear almost absurdly unscientific. And that’s what makes the eel unique. Science has come up against many mysteries, but few have proven as intractable and difficult to solve as the eel. Eels have turned out to be not only uncommonly difficult to observe—due to their strange life cycle, their shyness, their metamorphoses, and their roundabout approach to reproduction—but also secretive in a way that comes across as deliberate and preordained. Even when successful observation is possible, even when you get really close, the eel seems to pull away. Given the inordinate amount of time so many people have spent studying and trying to understand the eel, we should, simply put, know more than we do. That we don’t is something of a mystery. Zoologists call it “the eel question.”

  Aristotle may have been one of the first to document his misapprehensions about the eel, but he was, as we know, not the last. The eel has continued to elude scientific study into our modern era. Any number of prominent researchers, as well as amateurs with varying degrees of enthusiasm, have studied the eel without ever really understanding it. Some of the most noted names in the history of natural science have tried in vain to find the answer to the eel question. It’s as though their senses were not enough in themselves. Somewhere in the darkness and mud, the eel has managed to hide away from human knowledge. When it comes to eels, an otherwise knowledgeable humanity has always been forced to rely on faith to some extent.

  In the olden days, a distinction was likely often made between eels and other fish. The eel was a creature apart, with its appearance and behavior, its invisible scales and barely visible gills and ability to survive out of water. It was different enough to make many people believe it was in fact an aquatic snake or amphibian. Homer himself seemed to distinguish eels from fish. After Achilles kills Asteropaios in the Iliad he “let him lie where he was on the sand, with the dark water flowing over him and the eels and fishes busy nibbling and gnawing the fat that was about his kidneys.” Today, the question is still asked from time to time: Is the eel really a fish?

  This uncertainty about the fundamental nature of the eel has often led to some distance between us and them. People have found eels frightening or disgusting. They’re slimy and slithery, look like snakes and are said to eat human bodies; they move surreptitiously, in the dark and the mud. The eel is alien, unlike other animals, and regardless of how ubiquitous it has been, in our lakes and rivers and on our tables, it has always remained a stranger in some respects.

  The most abiding and debated mystery about the eel has been its method of reproduction. It’s only in the past century that we’ve been able to give a reasonable, if not conclusive explanation. For a long time, many people simply chose to believe Aristotle and his theory about worms springing into being spontaneously from mud. Others sided with the natural philosopher Pliny the Elder, who perished in the eruption of Mount Vesuvius in AD 79, and who claimed that the eel reproduced by rubbing itself against rocks, which freed particles from its body that in turn became new eels. Some believed the Greek author Athenaeuss, who in the third century explained that the eel secreted a kind of fluid that sank into the mud and became new life.

  More or less fanciful theories have been proposed throughout history. The ancient Egyptians were convinced eels sprang to life from nothing when the sun warmed the waters of the Nile. In various parts of Europe, it was thought that eels were born from decomposing vegetation on the seafloor or grew out of the rotting cadavers of other, dead eels. Some believed eels were born of sea-foam or created when the rays of the sun fell on a certain kind of dew that covered lakeshores and riverbanks in the spring. In the English countryside, where eel fishing was popular, most people adhered to the theory that eels were born when hairs from horses’ tails fell into water.

  Many of the different theories about the birth of the eel clearly revolve around a common notion. That is to say, the notion that life can spring from something seemingly lifeless, a minute echo of the birth of the universe itself. A mosquito born of a speck of dust, a fly born out of a piece of meat, an eel born of mud—such an idea has been commonly referred to as spontaneous generation and has historically been a widespread idea, particularly before the invention of the microscope. Simply put, people believed what they could see, so if you were looking at a piece of rotting meat and suddenly saw maggots crawl out of it, without having observed any flies or fly eggs, how could you conclude anything but that the larvae had been created out of thin air? In the same way, no human has observed procreating eels, and as far as anyone could tell, they had no reproductive organs.

  The idea of spontaneous generation leads back, of course, to the creation of everything, to the creation of life itself. If there was in fact once a beginning, when life sprung into existence from nothing (whether you attribute it to divine intervention or some other factor), it may not have been so outlandish to assume that such spontaneous generation could be repeated.

  How it supposedly happened has been explained several ways. In Genesis, there is mention of a “wind from God” sweeping across the barren, desolate earth, creating not only light and land and plants but all the animals, too. The ancient philosophers known as the Stoics spoke of pneuma, the breath of life, a combination of air and heat needed for the existence of both living bodies and the soul. The underlying premise is a belief that nonliving matter can be turned into living matter, that the living and the dead are in fact dependent on one another and that some kind of life can exist in something seemingly dead. When the eel could not be understood or explained, that kind of thinking was clearly close at hand; the eel became a reflection of the deeper mystery of life’s origins.

  What makes eels special, however, is that we’re still forced to rely on faith to some extent as we try to understand them. We may think we now know everything about the life and reproduction of the eel—its long journey from the Sargasso Sea, its metamorphoses, its patience, its journey back to breed and die—but even though that is all probably true and correct, much of it is nevertheless still based on assumption.

  No human has ever seen eels reproduce; no one has seen an eel fertilize the eggs of another eel; no one has managed to breed European eels in captivity. We think we know that all eels are hatched in the Sargasso Sea, since that’s where the smallest examples of the willow leaf–like larvae have been found, but no one knows for certain why the eel insists on reproducing there and only there. No one knows for certain how it withstands the rigors of its long return journey, or how it navigates. It’s thought all eels die shortly after breeding, since no living eels have ever been found after breeding season, but then again, no mature eel, living or dead, has ever been observed at their supposed breeding ground. Put another way, no human has ever seen an eel in the Sargasso Sea. Nor can anyone fully comprehend the purpose of the eel’s many metamorphoses. No one knows how long eels can live for.

  In other words, more than two thousand years after Aristotle, the eel remains something of a scientific enigma, and in many ways, it has become a symbol of what is sometimes referred to as the metaphysical. As it happens, metaphysics can also be traced back to Aristotle (though the concept was named only after his death). It is a branch of philosoph
y that is concerned with what exists outside, or beyond, objective nature, beyond what we can observe and describe with the help of our senses.

  Metaphysics is not necessarily concerned with God. It is, rather, an attempt to describe the true nature of things, the whole of reality. It claims there’s a difference between existence per se and the characteristics of that existence. It also claims the two questions are separate. The eel is. Existence comes first. But what it is, is a completely different matter.

  I like to think that’s why the eel has continued to be a source of fascination. Because that intersection between knowledge and faith, where knowledge is incomplete and therefore allowed to contain both fact and traces of myth and imagination, is compelling. Because even people who trust in science and an orderly natural world sometimes want to leave a small, small opening for the unknowable.

  If you are of the opinion that the eel should be allowed to remain an eel, it follows that you have to allow it to remain a mystery, to some degree. For now, at least.

  AND THE EEL DID REMAIN A MYSTERY. IS IT A FISH OR SOMETHING else entirely? How does it reproduce? Does it lay eggs or give birth to live young? Is it asexual? Is it hermaphroditic? Where is it born and where does it die? For centuries after Aristotle, the eel was the subject of countless theories, and every attempt to understand it was inevitably suffused with mystique. During the Middle Ages, two theories in particular were popular, often in combination: one that said the eel was viviparous, which is to say it gives birth to live young; another that said the eel was hermaphroditic, both male and female.

  With the resurgence of natural science in the seventeenth century, the eel question became the subject of more methodical inquiry. Aristotle’s methods were revived—especially his insistence on the need to systematically observe nature—and as a consequence, our view of the world, and the eel, changed.