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As their first assignment in Lynn Margulis's Environmental Evolution class, students sit in a little room on the third floor of Morrill Science Center, watching and listening as world-famous British chemist James Lovelock, originator of the Gaia hypothesis, discusses the environment of the Earth in relation to its sister planets.
Through the medium-tech media of a tape-player, a self-operated slide viewer, and a spindly robotic pen called an electrowriter, Lovelock's soft-spoken and witty narrative demonstrates how the chemical composition of the Earth's atmosphere became unique in its ability to sustain life. Slides of Mars and Venus clunk into view as Lovelock explains how the high level of oxygen and low level of carbon dioxide on Earth are not only necessary for life, but a product of it. In a later assignment, the unmanned pen of the electrowriter will scratch out a cybernetic sketch of the southwest coast of Australia biologist Stjepko Golubic's "blackboard notes" on the location of Shark Bay, home to the modern form of a rock-making bacteria that lived 3 billion years ago.
These interactive lectures by Lovelock and Golubic are but two of thirty such presentations in Margulis's collection. Gathered since the early 70s from among her wide-ranging acquaintance in the scientific world, these lectures are Margulis's way of putting her students in touch with the world's contemporary experts in astronomy, paleontology, geochemistry, microbiology, and ethnobotany. "If you want to understand Gaia," Margulis tells her students, "you should hear it from Lovelock, not me." In other words, if you want to understand the theory of relativity, you should hear it from Einstein. If he'd been a contemporary of Lynn Margulis, you'd probably be able to, electrowriter-notes and all.
The Gaia hypothesis introduces the unifying theme of Margulis's class: life as a geologic force. And although she takes no credit for the conception of the theory, she was instrumental in its development and acceptance into modern scientific culture. First published by Lovelock in the late 1960s, and named for the ancient Greek goddess of the Earth, the Gaia theory postulates that the living and non-living constituents of the Earth form a tightly coupled, interactive, self-regulating system. The Earth, Lovelock suggests, behaves like a pulsing, responsive amalgam of living beings. Or as Margulis puts it, the environment, far from being an inert physical system, "is a hotbed of activity where bacteria, fungi, protists, animals and plants construct, change, and regulate their surroundings." Unlike most biologists, Lovelock and Margulis do not believe living organisms simply adapt to their environments. They believe that the environment is instead shaped in part by the crystal-forming, temperature-changing, water-retracting, gas-producing organisms it sustains.
As is observed in The Spirit in the Gene, a new book by Reg Morrison for which Margulis has written the foreword, humans are perhaps the most alarming, but by no means the only, examples of organisms that shape their environment. Our bodies have not grown thick fur or learned to hibernate to meet the challenge of New England winters; we thrive here by creating a vast, durable infrastructure that protects our tender skin from February's cold. But buildings, even skyscrapers, are not a human invention. Our concrete monuments are paralleled by the stromatolites of Western Australia, the limestone towers described by Golubic in his resource-room "lecture" for Margulis's class. These modern-day "bacterial skyscrapers," as Margulis likes to call them, are representatives of a biological line dating as far back as 3.5 billion years; while today's four-to-five-foot-tall examples are huge by bacterial standards, ancient stromatolites were on the order of thirty feet high. And lithic structures are only one, relatively trivial example of how organisms effect the environment: If the Gaia theory is correct, life manipulates not only the landscape but major environmental factors such as temperature, oxygen level, and salt concentration in the oceans.
These are the factors and forces, actively controlled by the growth and metabolism of living organisms, with which the minds of Lynn Margulis and her students are occupied. With the help of teaching assistants Andrew Wier '95, '99G and organismic and evolutionary biology graduate student Adam Mouw, Margulis disabuses her Environmental Evolution classes of the notion that humans are Earth's only or even its most notable environmental choreographers. A lively lecture on stromatolites, for example, is interspersed with discussions of temperature-altering greenhouse gases that are produced much less by human pollution than by microbial respiration. And Margulis's students are pushed to see themselves in a realistic evolutionary context: A time-line assignment asks them to put human history into a linear representation of Earth's past. Margulis's favorite example of such a time-line comes from a book called Dinosaurs, Dunes and Drifting Continents by Richard Little of Greenfield Community College. In Little's model, Earth's history is mapped across the outstretched arms of a child, and all of human history can be effaced by a "single stroke with a medium-grained nail file."
Margulis's teaching tools are often, like this time-line, interactive, tactile, multi-sensory. Determined to avoid the slack-jawed daze that can be induced by sleeker forms of tutelage polished video presentations and the like she requires her students to literally confront the material. In addition to her library of medium-tech lectures by distinguished scientists, Margulis has stockpiled fossils and ancient rocks, paper-thin slide samples called petrographic sections, projection slides documenting the history of life on Earth. She has also written, largely for pedagogic purposes, the book Early Life, the first of its type to synthesize not only the evolution of nucleated cells from bacteria, but the effects those early microrganisms may have had on Earth's young environment. With Lorraine Olendzenski '93G, she edited the first edition of the Environmental Evolution textbook, published by MIT Press in 1992; she recently revised the textbook's second edition with entomology graduate student Aaron Haselton '97, and it will be ready for class in September 2000.
All of these resources are available to her students as study guides and audio-visual aids for the presentations that are crucial to the course. Unlike traditional college classes, Margulis's Environmental Evolution course eschews written examinations. Instead, students prepare and present up to five ten-minute talks elaborating or expanding on a topic covered in class. The final "oral exam" presentation is open to the public. After twenty-seven years of teaching, Margulis believes that the best demonstration of having understood an idea is the ability to explain it to others. In order to succeed in her class, students must be able to read and evaluate scientific material and to present it in much the same way as researchers present findings at scientific conferences.
Although she will not turn away a qualified and enthusiastic student, the unusual format of the class leads Margulis to limit it to "only as many students as fit around a table." She wants her students to face each other when they debate theories of evolution. A glorious cook, this member of the National Academy of Sciences and author of many books also wants to be able to feed all her students when they go on a field trip to, say, the Harvard forest: where, in between leaf-peeping and enjoying the bounty of their teacher's garden, the class in Environmental Evolution convenes to discuss well, life.