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Portrait of Lynn Margulis

Science · Biology

Lynn Margulis

1938–2011 · American

Evolutionary biology; microbiology

Lynn Margulis was an American evolutionary biologist best known for the endosymbiotic theory, which holds that mitochondria and chloroplasts in complex (eukaryotic) cells were once free-living bacteria engulfed by another cell. Her 1967 paper was rejected by many journals and long treated with scepticism, but the idea is now textbook biology. She also co-developed the Gaia hypothesis with James Lovelock and was married to the astronomer Carl Sagan.

How to spot them

  • ▸Endosymbiotic theory: mitochondria and chloroplasts descend from engulfed bacteria
  • ▸Gaia hypothesis, with James Lovelock
  • ▸First wife of Carl Sagan; mother of writer Dorion Sagan
  • ▸Five-kingdom classification in 'Five Kingdoms'

Key discoveries & works

Endosymbiotic theory of the origin of eukaryotic cells (1967)

Mitochondria and chloroplasts originated as free-living bacteria that came to live inside other cells

On the Origin of Mitosing Cells (1967)

Her landmark paper in the Journal of Theoretical Biology, published under the name Lynn Sagan

Origin of Eukaryotic Cells (1970)

Book-length development of her symbiosis theory

Five Kingdoms (with Karlene Schwartz) (1982)

Illustrated guide to the phyla of life classified into five kingdoms

Symbiotic Planet (1998)

Popular account of symbiosis as a driving force in evolution

Key ideas

  • Symbiogenesis: new kinds of organism can arise from the merger of different organisms, not only through gradual mutation
  • Gaia: living things and their environment form a self-regulating system

Quick-fire facts

  • •Born in Chicago; entered the University of Chicago as a teenager
  • •Married Carl Sagan in 1957; they had two sons, including the writer Dorion Sagan
  • •Spent much of her career at Boston University and then the University of Massachusetts Amherst
  • •Elected to the US National Academy of Sciences in 1983
  • •Received the US National Medal of Science in 1999
  • •Died at her home in Amherst, Massachusetts, on 22 November 2011, aged 73

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Sources