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Q&A | ideas

Were Aristotle and Thoreau ecologists?

Frank Egerton traces the early rumblings of a powerful human idea

We tend to think of the environment as a modern concern, and in many respects it is. As a political movement, environmentalism barely existed before the 1960s, and the word “ecology”—which gave scientists a way to talk about the interrelationships that drive the natural world—didn’t exist until the 19th century.

But long before that, ideas about relationships in nature were percolating through the culture, both in the West and elsewhere. Early evidence includes eighth century Arabic writings on zoology, Medieval European texts on falconry, descriptions of the life cycles of medicinal plants, and explorers’ accounts of North America’s flora and fauna.

Frank Egerton, a historian of science at University of Wisconsin-Parkside, has spent his career tracing this “prehistory” of ecology—looking for ways that ideas and observations we’d now see as ecological first surfaced in science, philosophy, and literature. In a new book, “Roots of Ecology,” he takes a novel approach to the topic: He begins in antiquity and ends when the term was coined by German scientist Ernst Haeckel in 1866.


In examining the long human engagement with “ecology,” Egerton finds thinkers drawing specific connections between organisms and the environment without a larger framework to place them in. It was Darwin’s writings that would finally help crystallize the bigger idea: Haeckel realized that evolutionary theory could give rise to a new science of understanding how plants and animals lived, interacted, and were affected by their environment, and this science needed a word of its own. From then on, scientists would no longer simply catalog life as natural historians had: They would grapple with humanity’s place in the environment and the complex balance of ecosystems.

The idea of ecology has turned out to be a profoundly important one. Ecological questions lie at the center of some of our most challenging problems, such as responding to urbanization, climate change, and loss of habitat. The term has since made its way into areas beyond biology: We now talk about the ecology of business, politics, and social relationships. Egerton spoke with Ideas by phone about its deepest roots.

IDEAS: How far back have you been able to trace the notion of ecology?


EGERTON: There are a lot of ecological insights in [the writings of Aristotle]. I wanted to trace those back further, and I traced it back to this “balance of nature” concept. That concept came from two people. One of them, Herodotus, was a historian, and Plato was a philosopher. Herodotus said that predatory animals have fewer offspring than the animals they eat—there are provisions so that they don’t eat up all their food. And Plato said each species has a means of protection so it doesn’t go extinct.

IDEAS: So they were looking for ways to explain why species survive over time?

EGERTON: Yes, the deer can outrun the wolf usually, not always, so the wolves will never catch them all....Aristotle, although he himself did not draw upon the balance of nature concept, he does have other ecological observations in his writing. One of these is what we now call symbiosis....The example that he gives is that there’s a clam in the ocean and there’s a little crab that lives inside of it. The crab seems to get some nourishment from it, and the crab might also protect the clam.

IDEAS: What about relationships between organisms and their environment?

EGERTON: Earlier people didn’t think a lot about the environment. They knew it was cooler in the north than at the equator…but they didn’t think it was important to study the environment. Alexander von Humboldt around 1800 was the first one to actually measure environmental factors in relation to plants and animals. [His survey of Chimborazo and Cotopaxi] was the most important diagram for ecology in the 1800s. There are 10 columns of data on each side of the map showing changes as one ascended the mountain....He also noted the plants and animals found at each elevation and wrote those names on the cutaway of the mountain so that one could use a ruler to locate the data on the sides for each species at that elevation.


IDEAS: You call Thoreau an ecologist, although he had little scientific training and lived before the term ecology existed. Why?

EGERTON: He didn’t name it, but he did understand that it was needed. He was quite interested in the way that the squirrels interacted with the oak tree—that the oak tree provides food for the squirrel but the squirrel stores up food for the winter, and it always buries more acorns than it ever digs up. The squirrel is planting the acorns for the oak tree while he’s eating some of them. [Thoreau] was the first one that discovered that. He actually made the first ecological survey of a lake, probably in the world.

IDEAS: Once Ernst Haeckel defined the field, how did ecologists distinguish themselves from naturalists?

EGERTON: Natural history had been a flourishing enterprise, and they thought of natural history as sort of an old fashioned version of ecology. They wanted to distinguish ecology because it has hypotheses that it investigates, and then it develops theories....What is it that makes plants grow? It’s light and it’s heat and it’s water, and also some minerals from the earth. They had to isolate all of these things rather than just describing the plants that do grow. Experimentation was an early aspect to ecology.


IDEAS: When did this science start becoming a public issue?

EGERTON: Ecology hit the big time with the public in the 1960s. At that time, the word was used interchangeably with environment. So you could hear someone say “help preserve our ecology” when they were really talking about the environment.

IDEAS: How exactly are they different?

EGERTON: Environment is the surroundings, and ecology is a particular science that studies organisms in their surroundings. So they’re very different kinds of concepts—one is a science, and the other is a factor you study in nature.

IDEAS: And it took on new importance in the 20th century.

EGERTON: Ecology was a fairly small science in terms of the number of people involved until World War II. The Atomic Energy Commission became interested in funding ecology research because it wanted to know the effect of radiation on plants and animals. Ecology has become the guide for conservation—if you want to conserve a particular species, well you can’t do that unless you understand its ecology. And it’s also a guide to public health in a sense, because we live in an environment and it affects our health.

Courtney Humphries is a freelance writer in Boston and the author of “Superdove: How the Pigeon Took Manhattan...And the World.”