Snyder Lecture

Chance had little to do with how we got where we are, biologist says

Ever since the most distance reaches of primordial times, life on Earth has been driven by a complex dance between organisms and the environment, according to evolutionary biologist Lynn Margulis.

Lynn Margulis © ALONSO NICHOLS

“What organisms do is actively maintain and regulate the environment to which they respond—which then changes the environment,” she said during the annual Richard E. Snyder Presidential Lecture at Tufts on October 4. “It’s a dialogue, not a monologue, and,”—here Margulis modulates her voice for emphasis—“it’s not by chance alone.”

Margulis’ rejection of “chance”—or the appearance of random genetic mutation—as a pivotal point in the evolutionary process, and her adherence to an alternate view known as symbiogenesis, which postulates that new species evolve through the fusion of different types of organisms, set her outside the scientific mainstream for decades. Now her ideas are widely accepted, and she has been honored many times over, both by her peers and the academy. (Tufts awarded her an honorary doctor of science degree during its 2006 commencement ceremonies.)

Which leads to her appearance at Tufts as the Snyder Presidential Lecturer, a spot reserved for those who have challenged conventional wisdom in their fields; speakers are chosen independently by President Lawrence S. Bacow. Margulis, the first woman chosen as a Snyder speaker—“but not the last,” Bacow promised—is a Distinguished University Professor in the Department of Geosciences at the University of Massachusetts at Amherst.

She delivered a talk that was part science, part poetry: “But nature is a stranger yet; / the ones that cite her most / Have never passed her haunted house, / Nor simplified her ghost …That those that know her, know her less / The nearer her they get,” she recited to the audience at Cabot Auditorium—inspired as much by Emily Dickinson as by slides of paramecium and bacteria.

Her work maintains that the genetic variation inherent to evolution results primarily from the interaction and integration of living organisms and their environment—with a small degree of random mutation involved. This challenges a central tenet of the school of thought known as neo-Darwinism, which held sway for much of the 20th century.

Evolution, said Margulis, is “a word Darwin never used … but we all know that he showed very conclusively, in the opinion of most people who are rational and well-read, that all life on Earth today comes from common ancestry.”

Regulation by consensus
How those modifications came about is the matter at hand. Margulis draws on James E. Lovelock’s “Gaia” hypothesis, which holds that the Earth’s surface forms a physiological living system.

For example, she said, the Earth’s atmosphere is not in “chemical equilibrium,” with “way too much oxygen and way too little carbon dioxide.” How to explain this? “You can believe that an omnipotent engineer, the divinity, made just enough oxygen for us,” she said. “Or you can believe, as many neo-Darwinists do, that it’s by chance alone. Or, you can go with the Gaia hypothesis that says these are features actively regulated by the consensus of organisms of the surface.”

And, Margulis stressed, the most important phase of evolution took place during the Earth’s earliest years, the Precambrian era, which began about 4,500 million years ago. This era is too often overlooked by researchers because its life forms are considered too primitive, she said. In her view, she said, “everything important evolved” at that farthest point.

Margulis has made a career of pushing boundaries and transcending disciplines. She entered the University of Chicago at age 14. She holds a master’s from the University of Wisconsin and a Ph.D. from the University of California at Berkeley. She is the author of numerous books, including scholarly works, essays and a novel. She was elected to the National Academy of Sciences in 1983 and received the Presidential Medal of Science from Bill Clinton in 1999. The Library of Congress announced in 1998 that it will permanently archive her papers.

Helene Ragovin is a senior writer in Tufts’ Office of Publications. She can be reached at This story ran in the November 2007 issue of the Tufts Journal.