Biologist. First formulated endosymbiotic theory, stating that
eukaryotic organisms began as
prokaryotes that were engulfed by other prokaryotes and continued to live in a
symbiotic relationship. Now working on the
Gaia hypothesis (her spelling), which considers the entire
earth as an organism.
She received her Ph.D. from the University of Calfornia, Berkeley in 1963 and is currently a Distinguished University Professor at the University of Massachusetts, Amherst.
(Source: http://marlin.bio.umass.edu/faculty/biog/margulis.html)