Lynn Margulis

Lynn Margulis (born Lynn Petra Alexander; March 5, 1938 – November 22, 2011) was an American evolutionary biologist, who was the primary modern proponent for the significance of symbiosis in evolution. In particular, Margulis transformed and fundamentally framed biologists' understanding of the evolution of the Eukaryotes, organisms with nuclei in their cells. She proposed that they came into being by symbiotic mergers of bacteria. Margulis was the co-developer of the Gaia hypothesis with the British chemist James Lovelock, proposing that the Earth functions as a unified self-regulating system, and the principal defender and promulgator of the five kingdom classification of Robert Whittaker. Throughout her career, Margulis' work could arouse intense objections, and her formative paper, "On the Origin of Mitosing Cells", appeared in 1967 after being rejected by about fifteen journals. Still a junior faculty member at Boston University at the time, her theory that cell organelles such as mitochondria and chloroplasts were once independent bacteria was largely ignored for another decade, becoming widely accepted only after it was powerfully substantiated through genetic evidence. Margulis was elected a member of the US National Academy of Sciences in 1983. President Bill Clinton presented her the National Medal of Science in 1999. The Linnean Society of London awarded her the Darwin-Wallace Medal in 2008. Margulis was a strong critic of neo-Darwinism. Her position sparked lifelong debate with leading neo-Darwinian biologists, including Richard Dawkins, George C. Williams, and John Maynard Smith. Margulis' work on symbiosis and her endosymbiotic theory had important predecessors, going back to the mid-19th century – notably Andreas Franz Wilhelm Schimper, Konstantin Mereschkowski, Boris Kozo-Polyansky, and Ivan Wallin – and Margulis not only promoted greater recognition for their contributions, but personally oversaw the first English translation of Kozo-Polyansky's Symbiogenesis: A New Principle of Evolution, which appeared the year before her death. Many of her major works, particularly those intended for a general readership, were collaboratively written with her son Dorion Sagan. In 2002, Discover magazine recognized Margulis as one of the 50 most important women in science.

Early life and education Lynn Petra Alexander was born on March 5, 1938 in Chicago, to a Jewish family. Her parents were Morris Alexander and Leona Wise Alexander. She was the eldest of four daughters. Her father was an attorney who also ran a company that made road paints. Her mother operated a travel agency. She entered Hyde Park High School in 1952, describing herself as a bad student who frequently had to stand in the corner. A precocious child, she was accepted at the University of Chicago Laboratory Schools at the age of fifteen. In 1957, at age 19, she earned a BA from the University of Chicago in Liberal Arts. She joined the University of Wisconsin to study biology under Hans Ris and Walter Plaut, graduating in 1960 with an MS in genetics and zoology. (Her first publication, published with Plaut in 1958 in the Journal of Protozoology, was on the genetics of Euglena, which are flagellates that have features of both animals and plants.) She then pursued research at the University of California, Berkeley, under the zoologist Max Alfert. Before she could complete her dissertation, she was offered research associateship and then lectureship at Brandeis University in Massachusetts in 1964. It was while working there that she obtained her PhD from the University of California, Berkeley in 1965. Her thesis was An Unusual Pattern of Thymidine Incorporation in Euglena.

Career In 1966 she moved to Boston University, where she taught biology for twenty-two years. She was initially an Adjunct Assistant Professor, then was appointed to Assistant Professor in 1967. She was promoted to Associate Professor in 1971, to full Professor in 1977, and to University Professor in 1986. In 1988 she was appointed Distinguished Professor of Botany at the University of Massachusetts at Amherst. She was Distinguished Professor of Biology in 1993. In 1997 she transferred to the Department of Geosciences at UMass Amherst to become Distinguished Professor of Geosciences "with great delight", the post which she held until her death.

Endosymbiosis theory

In 1966, as a young faculty member at Boston University, Margulis wrote a theoretical paper titled "On the Origin of Mitosing Cells". The paper, however, was "rejected by about fifteen scientific journals," she recalled. It was finally accepted by Journal of Theoretical Biology and is considered today a landmark in modern endosymbiotic theory. Weathering constant criticism of her ideas for decades, Margulis was famous for her tenacity in pushing her theory forward, despite the opposition she faced at the time. The descent of mitochondria from bacteria and of chloroplasts from cyanobacteria was experimentally demonstrated in 1978 by Robert Schwartz and Margaret Dayhoff. This formed the first experimental evidence for the symbiogenesis theory. The endosymbiosis theory of organogenesis became widely accepted in the early 1980s, after the genetic material of mitochondria and chloroplasts had been found to be significantly different from that of the symbiont's nuclear DNA. In 1995, English evolutionary biologist Richard Dawkins had this to say about Lynn Margulis and her work:

I greatly admire Lynn Margulis's sheer courage and stamina in sticking by the endosymbiosis theory, and carrying it through from being an unorthodoxy to an orthodoxy. I'm referring to the theory that the eukaryotic cell is a symbiotic union of primitive prokaryotic cells. This is one of the great achievements of twentieth-century evolutionary biology, and I greatly admire her for it.

Symbiosis as evolutionary force

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