Lynn Margulis

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Evolutionary biologist Lynn Margulis transformed the way we think about the origins of life. Eukaryotic (plant, animal, and fungal) cells contain membrane-bound “organelles” that are not present in bacterial cells. In her groundbreaking endosymbiotic theory of organogenesis, Margulis proposed a mechanism by which these organelles, including mitochondria (cellular “powerhouses”) and chloroplasts (plants’ photosynthetic factories), began as bacterial cells taken in (endosymbiosed) by other cells. After being endosymbiosed, these bacteria evolved to fulfill the energy needs of the host cell. This theory was incredibly controversial at the time (fourteen publishers rejected it before it was finally published) but genetic and experimental evidence has provided strong support for it, and it is now widely accepted.

Margulis was born in Chicago in 1938. She earned a Liberal Arts degree from the University of Chicago followed by a master’s in genetics and zoology from the University of Wisconsin before going on to obtain a PhD from the University of California, Berkeley. She taught for almost two decades at Boston University before transferring to the University of Massachusetts at Amherst. Margulis’ initially controversial endosymbiotic theory turned out to be one of her least controversial hypotheses; described by many as a “scientific rebel,” she spoke out against “Neo-Darwinists” who believe that evolution occurs linearly through small changes within an organism, arguing instead that exchange of genetic material between different organisms plays a larger role than Neo-Darwinists give credit to.

Despite often thriving among scientific “outcasts,” Margulis also received recognition from the more mainstream scientific community; she was elected to the US National Academy of Sciences in 1983 and received the National Medal of Science in 1999. Margulis passed away in 2011 from complications of a stroke, but her son, Dorion Sagan, with whom she wrote many books, continues her legacy of communicating science.