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Home , Lynn Margulis

RETROSPECTIVE

Lynn Margulis, 1938–2011

Andrew H. Knoll1 Department of Organismic and Evolutionary , Harvard University, Cambridge, MA 02138

n November 22, 2011, Lynn students also benefitted from her engaging Margulis, visionary biologist and presence and enthusiastic support. I was tireless champion of the micro- one of them, both stimulated to study the O ’ bial world, died of a massive early by Lynn s writings and from . Born in 1938, Lynn was intellec- my first year of graduate school, welcomed tually precocious, earning her bachelor’s as friend and colleague. degree from the University of at In my favorite memory of Lynn, she is age 18 and a Berkeley PhD 6 years later. crawling on the floor with my infant Lynn’s enduring place in science was daughter, both of them giggling away. The earned soon thereafter, with the publica- maternal instinct was strong in Lynn, and tion of her theory of endosymbiosis, a it extended beyond her beloved children radical and, as it turned out, lasting and the children of her friends. In a very real explanation for the origin of mitochon- sense, students and colleagues who were dria and , the curious about science were all her children. responsible for energy metabolism in Lynn was also part evangelist, ceaselessly eukaryotic cells. In Lynn’s view, the championing as the underap- originated as a free-living preciated architects of Earth’s biosphere. cyanobacterium engulfed by a protozoan After two decades on the faculty of Reprinted with permission from the University of Advancing Technology, Technology, of Advancing the University with permission from Reprinted ceremony. Thinking award Vinci the study of Society for da Leonardo and reduced through time to metabolic , Lynn moved to the slavery. Similarly, she hypothesized Lynn Margulis. University of , where she was that the descended from Distinguished University Professor at the an endosymbiotic bacterium capable of time of her death. Her research earned her aerobic respiration. Unbeknownst to able view of eukaryotic numerous honors, including the Darwin– Lynn at the time, the Russian biologist stands as one of the great advances in 20th Wallace Medal of the Linnean Society, the Konstantin Merezhkovsky had published century science. Throughout her life, Lynn National Medal of Science, and member- a similar proposal as early as 1905. maintained as well that the flagellum, the ship in the National Academy of Sciences. However, Merezhkovsky’s ideas were whip-like structure responsible for loco- Her books, several written with her son largely ridiculed or forgotten, and when motion in many eukaryotic cells, also , include Origin of Eukaryotic Margulis resurrected them, criticism originated as a symbiotic bacterium, but Cells, Microcosmos, Five Kingdoms: An was harsh. Some 15 journals rejected this theory has never garnered strong Illustrated Guide to the Phyla of Life on her first paper on endosymbiosis be- support from other biologists. Earth, and Acquiring Genomes: A Theory of fore it found a home in Journal of Endosymbiotic theory was only the be- the Origins of Species (2–5). Marriages to Theoretical Biology (1). ginning of Lynn’s unconventional career. in 1958 and Nicholas Margulis However, Margulis did more than She was an early advocate of the Gaia Hy- in 1965 ended in divorce. Lynn is sur- rediscover endosymbiotic theory; she pothesis, ’s proposal that vived by her children Dorion Sagan, restated it in the then emerging language of life actively regulates Earth’s environment. Jeremy Sagan, Zachary Margulis, and cell and molecular biology, opening the Indeed, endosymbiosis and Gaia were Jenny Margulis. idea to scientific test. In time, cell biologists linked in Lynn’s mind as components of a Lynn Margulis will long be remembered showed that the chloroplast and mito- coherent alternative biology based on co- as a fountain of ideas—fertile, original, in- chondrion are isolated from the rest of the operation rather than competition. This spiring, contentious, and unedited. Lynn cell by a set of enveloping membranes; view led Lynn to reject basic tenets of evo- could infuriate her colleagues, but at least moreover, both organelles contain DNA, lutionary theory, bringing her into lasting one of her proposals changed the way that previously thought to be restricted to the conflict with evolutionary biologists. Today, we think about life. In conversation, Lynn nucleus. These observations set up the most biologists accept an expanded role for seemed always to have the last word, and I crucial test of Lynn’s hypothesis. Com- cooperation in ecology and evolution, but am happy to grant it one last time. Earlier parisons of nucleotide sequence in genes few endorse Lynn’s view that this year, in a comment that could stand as from the chloroplast showed it to be re- drives speciation. She courted controversy her epitaph, Lynn told an interviewer from lated most closely to free-living cyano- until the end, questioning the role of HIV in Discover magazine, “I don’t consider my bacteria, not to nuclear DNA of the same causing AIDS in recent years. ideas controversial. I consider them right.” cell. Also, mitochondria were shown to Throughout her life, Lynn championed nest within the proteobacteria, another science education, especially in less de- bacterial clade. Lynn was right: the eu- veloped countries. Fluent in Spanish, she karyotic cell is a committee, built through was revered by students in Spain and Latin Author contributions: A.H.K. wrote the paper. evolution by the merger of distinct ge- America for her unflagging efforts to help The author declares no conflict of interest. nomes. To many biologists, this remark- them learn. Generations of American 1E-mail: [email protected].

1. Sagan L (1967) On the origin of mitosing cells. J Theoret 3. Margulis L, Sagan D (2002) Acquiring Genomes: A 5. Margulis L, Sagan D (1986) Microcosmos: Four Billion Biol 14:255–274. Theory of the Origins of Species (Perseus, New York). Years of Evolution from our Microbial Ancestors 2. Margulis L (1970) Origin of Eukaryotic Cells (Yale Uni- 4. Margulis L, Schwartz KV (1982) Five Kingdoms: An Il- (Summit, New York). versity Press, New Haven, CT). lustrated Guide to the Phyla of Life on Earth (WH Freeman, San Francisco).

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