Full Speed Ahead
By James di Properzio
Photography by Dan Dry
and undeterred, biologist Lynn Margulis, AB’57, has seen some
of her once-revolutionary ideas on evolution win mainstream acceptance.
As for the rest, she’s still pressing on.
On a cold November morning in Amherst, Massachusetts,
Lynn Margulis, 65 years old and without a helmet, is riding her
secondhand Miyata 10-speed—its two side baskets full of books,
mail, and lunch—down the sidewalk to her laboratory at the
University of Massachusetts, where she holds the title Distinguished
University Professor in the Department of Geosciences. At 6 a.m.
it is barely light, shops are closed, and the town is quiet. But
Margulis, a short, graying dynamo, confides, “I do my best
work when no one is around.”
Her best work isn’t bad: elected to the
National Academy of Sciences in 1983 and awarded the National Medal
of Science in 1999, Margulis has her ninth book behind her (the
paperback edition of Acquiring Genomes: A Theory of the Origins
of Species was published in July 2003), more than 200 scientific
articles, and dozens of popular essays to her name. This week Margulis,
AB’57, also has a to-do list that includes carrying out lab
work with termite protists; publishing research on symbiotic bacteria;
shopping for an American publisher for her novel about love and
scientists, Luminous Fish; finishing a book on pioneering
landscape architect and ecologist Ian L. McHarg; and creating lecture
On today’s agenda at the Morrill Science
Center is the premiere of her new teaching video, Green Animals.
After Margulis cues up the tape and fields questions from the 30-some
advanced undergraduates, graduate students, and professors, Green
Animals begins its up-close and technical footage of sea slugs
(naked-eye views of whole slugs give way to highly-magnified microscopic
frames). These are no ordinary images and no ordinary slugs—they
are living proof of her most famous theory.
I grew up on the
South Side of Chicago,” Margulis says of braving the
morning’s bitter chill on her bicycle. “I’m not
afraid of anything.” Indeed, Margulis boldly makes claims
that fly in the face of accepted scientific thought. As the self-appointed
spokesperson for the 250,000 extant species of microorganisms, she
has made foundational contributions to modern biology. Once thought
outrageously heterodox, her theory of symbiosis as an evolutionary
mechanism—the “endosymbiotic hypothesis,” which
posits that the ancestors of mitochondria in animal cells and the
plastids in algae and plants were once free-living organisms—is
now considered fundamental to understanding evolution.
Margulis also made an important contribution
to taxonomy with the 1982 publication of Five Kingdoms.
With coauthor Karlene V. Schwartz, then a UMass–Boston biology
instructor, she literally rewrote the book on classification, discarding
the old plant/animal system that tried to cram hundreds of millions
of microscopic beings into the two kingdoms of organisms visible
to the naked eye. Through her work on microbes’ interactions
with sedimentary rocks and atmospheric chemistry—and vice
versa—she has provided support for James Lovelock’s
Gaia hypothesis, the theory that Earth’s biota, working in
concert with its environment, acts as a single, self-regulating
living system maintaining conditions that are suitable for life.
Her latest research, presented in Acquiring Genomes (Basic
Books, 2002), cowritten with son Dorion Sagan, concerns what she
calls symbiogenesis—a kind of horizontal evolution in which
new species occur through symbiosis, as temporary partnerships between
organisms grow into more permanent relationships.
“Scientists are mostly instrumentalists,
but she’s an innovator—often ahead, not always right,
but right enough of the time,” says Peter H. Raven, director
of the Missouri Botanical Gardens and author of a number of standard
biology texts. Margulis’s championing of the symbiotic theory
of cell evolution, Raven says, “marks her as someone who has
made an extraordinary contribution, a revolution in thinking about
the cell—and it is nothing less than a revolution.”
her science, Margulis’s personal life is anything but conventional.
The mother of four and the grandmother of seven mountain climbs,
in-line roller-skates, cross-country skis, and bicycles regularly.
In the summer she skinny-dips in a secluded pond on the outskirts
of town every evening after work, marveling at the dam-building
beavers that share the water with her. Married and divorced twice,
she has had a personal and research partnership with her “compañero,”
University of Barcelona microbiologist Ricardo Guerrero, for more
than 20 years.
Born in Chicago in 1938, Lynn Alexander, along
with her three siblings, attended the University’s Laboratory
Schools; she applied to the College at age 14. Self-described as
bossy, rude, hyperactive, and self-centered, she was eager to get
away from home, where her parents, an attorney and a housewife,
were socialites and drinkers. “They did everything I can’t
stand,” Margulis exclaims.
She enrolled in the College at 16 and that same
year, while heading up the Eckhart Hall stairs, she met a 19-year-old
physics grad student on his way down. “Everyone knew who he
was,” Margulis recalls of Carl Sagan, AB’54, SB’55,
SM’56, PhD’60, who would become a professor of astronomy
at Cornell University, the host of the TV show Cosmos,
and a well-known popularizer of science. Sagan was tall, handsome,
and articulate, and it was love in an instant. Three years later,
on June 16, 1957, the week after she received her bachelor’s
degree, they were married. The couple had two sons—Dorion,
a writer, born in 1959, and Jeremy, a music-software developer and
composer, born in 1960.
While fascinated by Sagan’s interest in
astronomy, it was not his influence that started her on a science
career. She had come to the University hoping to be a writer. As
she details in the autobiographical Symbiotic Planet (Basic
Books, 1998), Margulis locates her initial impetus toward science
in a single course: Natural Science 2, required as part of the Common
Core. Nat. Sci. 2 entailed reading primary sources, and Gregor Mendel’s
classic experiments on breeding garden peas drove Margulis to learn
as much as she could about heredity and genetics.
It wasn’t until she was 19 and in graduate
school, studying genetics at the University of Wisconsin–Madison
under Walter Plaut, that Margulis first saw amoebae—through
the phase-contrast microscopes in Plaut’s laboratory. “I
really liked amoebae,” she laughs. “I still do.”
She got to see them at close range, siphoning out dead ones with
the dirty water, then adding salt solution and food. Margulis recalls
this task fondly: “I owe my passion for working on Saturday
nights to the utter necessity of amoebae feeding and bowl cleaning
While working in Plaut’s lab and earning
a master’s degree in zoology-genetics, she was intrigued by
the curiously independent nature of mitochondria and became a proponent
of endosymbiosis—a theory first introduced in the 1920s—that
would come to have a profound influence on all of her later research.
Endosymbiosis occurs when one organism takes up permanent residence
in another, creating a single functional organism.
An example of endosymbiosis can be seen in Margulis’s
Green Animals video as the sea slugs pierce algae and keep
the algae’s chloroplast, or energy-making cells, alive in
their translucent gut. There the plastids photosynthesize and supply
the slugs’ nutriment, while the slugs in turn provide an ideal
environment for the plastids. Examining the slug’s genome
reveals a gene for a protein useless to animals. Somehow the gene,
otherwise found only in algae, has been passed from the algal to
the slug’s cells.
On a larger scale, endosymbiosis suggests that
both the mitochondria of animal cells and the chloroplasts of plant
cells, both of which have independent genomes totally unlike the
genomes of their host cells, were originally free-living bacteria
engulfed by other cells but not digested. The bacteria stayed on,
giving their hosts the chemical energy they needed to be healthier
and more vigorous, and in turn received what they required from
the host (and, in the case of chloroplasts, the sun).
Margulis’s major theoretical and interpretive
work since then has radiated from the concept of integral symbiosis:
a reunderstanding of the kingdoms of life and their relationships.
Symbiosis is not limited to the level of chloroplasts and sea slugs:
the entire ecosystem of the planet in physical contact with the
air is one great symbiosis as seen from space. As life produces
oxygen and other reactive gases, it fosters its own environment.
For Margulis, much of evolution is thus a symbiotic endeavor in
which interaction and merger lead to persistence.
Her fascination with symbiosis, however, did
not bring her immediate success. Her 1967 paper “Origin of
Mitosing Cells” was ignored or rejected by more than 20 publishers—although
it later generated 800 reprint requests, won the Boston University
faculty publication award, and formed the basis for her first book,
Origin of Eukaryotic Cells: Evidence and Research Implications
for a Theory of the Origin and Evolution of Microbial, Plant and
Animal Cells on the Precambrian Earth (Yale University Press,
After Sagan was offered a postdoc at the University
of California, Berkeley, the family moved to Oakland, and Margulis
continued her doctorate. Unable to spend a required semester at
a marine laboratory because of the demands of childcare, she ended
up focusing on genetics with a zoology thesis director, Max Alfert.
Alfert was a formidable mentor: “He graduated almost no one,”
Margulis says. When Sagan joined Harvard’s astronomy department
in 1963, she left Berkeley with her dissertation almost completed.
Difficulties in convening her committee kept her from filing for
her degree until 1965, after she had published her thesis, “Unusual
Pattern of Thymidine Incorporation in the Cytoplasm of Euglena,”
in the Journal of Protozoology.
Margulis lectured and worked in labs at Brandeis
University before landing a part-time job in Boston University’s
biology department, where she went from adjunct to full professor
in ten years. Although she’d agreed to give her marriage a
final, three-month try in Boston, she found the needs of two small
children and an equally demanding husband overwhelming, and in 1964
she and Sagan divorced. (Although they saw each other infrequently,
they remained colleagues and friends until Sagan’s 1996 death.)
In Boston she met her second husband, Thomas
N. Margulis, an X-ray crystallographer teaching at Brandeis. Her
third son, Zachary, now a lawyer in New York City, was born in 1967,
and her daughter, Jennifer, a writer, was born in 1969. But again,
marriage proved a struggle. “I quit my job as a wife twice,”
she says of her second divorce, which came 13 years after Jennifer’s
birth. “It’s not humanly possible to be a good wife,
a good mother, and a first-class scientist. No one can do it—something
has to go.”
Indeed, ever since Chicago’s fixed curriculum
introduced her to biology, she has suffered the tension of balancing
science and personal life. Two years ago the Spanish publisher Tusquets
brought out her novel exploring this tension, Luminous Fish,
a group of stories following the interconnected lives of several
scientists across the globe as their dedication to research tears
at their love lives and families. The book, translated by Vicente
Campos, has sold well, but she is still seeking a publisher for
the English original.