The Revolutionary Biologist Who Transformed Our Understanding of Life
Journal Rejections
Billion Years of Evolution Explained
Revolutionary Theory
In the history of science, few stories are as compelling as that of Lynn Margulis—a brilliant biologist whose revolutionary ideas about the cooperative nature of life were initially rejected by the scientific establishment, only to become foundational principles of modern biology.
When Margulis first proposed that complex cells originated through symbiotic mergers of bacteria, her paper was rejected by fifteen journals before finally seeing publication in 19671 . One reviewer even told her, "Your research is crap"6 . Yet through what Richard Dawkins would later call "sheer courage and stamina," she persevered, ultimately transforming our understanding of how life evolves and interacts1 .
Margulis championed the then-radical idea that evolution progressed as much through cooperation and symbiosis as through competition—a vision that contrasted sharply with the dominant neo-Darwinian perspective of her time6 8 .
Born in Chicago, Illinois
Publishes groundbreaking paper after 15 rejections
Expands theory in "Origin of Eukaryotic Cells"
Elected to National Academy of Sciences
Awarded National Medal of Science
Passes away at age 73
The Endosymbiotic Theory
Margulis's most celebrated contribution, the serial endosymbiotic theory (SET), proposed that eukaryotic cells (the complex cells that make up plants, animals, and fungi) originated through a series of symbiotic mergers between different types of bacteria.
She hypothesized that approximately two billion years ago, ancient prokaryotic cells engulfed certain bacteria but didn't digest them—instead, they established permanent, mutually beneficial relationships that evolved into the specialized organelles we recognize in cells today1 .
Though initially controversial, Margulis's theory began gaining traction as new genetic evidence emerged. The discovery that mitochondria and chloroplasts contained their own DNA, distinct from the DNA in the cell's nucleus, provided critical support for her idea1 .
Even more convincing was the finding that the DNA in these organelles more closely resembled bacterial DNA than the nuclear DNA of eukaryotic cells7 .
For more than a decade after Margulis published her revolutionary theory, it remained on the fringes of biological thought. The turning point came in 1978 when Robert Schwartz and Margaret Dayhoff published a groundbreaking study comparing the genetic material of organelles to that of various bacteria1 7 .
Their work provided the first compelling molecular evidence supporting Margulis's once-radical proposal.
Schwartz and Dayhoff's approach focused on comparing genetic sequences across different organisms. Their experimental procedure followed these key steps:
| Genetic Feature | Mitochondrial Similarity to Bacteria | Chloroplast Similarity to Cyanobacteria |
|---|---|---|
| Ribosomal RNA sequences | High similarity to α-proteobacteria | High similarity to cyanobacteria |
| Gene organization | More similar to bacterial genomes | Nearly identical in some regions |
| Translation machinery | Bacterial-like | Bacterial-like |
| Antibiotic sensitivity | Similar to bacteria | Similar to cyanobacteria |
| Year | Event | Significance |
|---|---|---|
| 1967 | Margulis publishes "On the Origin of Mitosing Cells" | Theory initially rejected or ignored by most scientists |
| 1970 | Margulis expands theory in "Origin of Eukaryotic Cells" | Presents comprehensive evidence for endosymbiosis |
| 1978 | Schwartz & Dayhoff publish genetic evidence | Provides first molecular confirmation of theory |
| Early 1980s | Theory gains widespread acceptance | Becomes new biological paradigm |
| 1999 | Margulis awarded National Medal of Science | Official recognition of her contribution |
Research into endosymbiotic relationships requires specialized methods and materials
| Tool/Method | Function | Application in Endosymbiosis Research |
|---|---|---|
| Electron microscopy | High-resolution imaging of cellular structures | Revealed structural similarities between organelles and bacteria |
| DNA sequencing | Determining genetic code | Allowed comparison of organelle and bacterial genomes |
| PCR amplification | Copying specific DNA segments | Enabled study of rare genes in organelles |
| Ribosomal RNA analysis | Evolutionary comparison using conserved genes | Provided "molecular clock" for dating evolutionary divergences |
| Antibiotic sensitivity testing | Assessing response to bacterial inhibitors | Showed organelle translation resembles bacterial systems |
| Fluorescence in situ hybridization | Visualizing specific genetic sequences | Confirmed location and organization of organelle DNA |
These tools collectively enabled scientists to move beyond morphological observations to the genetic and molecular evidence that ultimately validated Margulis's theory.
Margulis faced intense opposition throughout much of her career, with her work frequently attracting "intense objections" from leading biologists1 . Her formative paper was rejected by approximately fifteen journals before appearing in the Journal of Theoretical Biology in 19673 .
This resistance stemmed from several factors:
Despite the initial resistance, Margulis lived to see her ideas become widely accepted and celebrated. Her perseverance earned her some of science's highest honors:
Presented by President Bill Clinton in 19991
Elected in 19831
Awarded by the Linnean Society of London in 20081
Margulis's scientific contributions extended far beyond explaining the origin of organelles
Together with biologist Karlene V. Schwartz, Margulis developed a comprehensive five-kingdom classification system that organized life into animals, plants, bacteria (prokaryotes), fungi, and protoctists.
This system rejected the traditional protist kingdom as too general.
Margulis continued to develop and expand her symbiotic view of evolution throughout her career. She argued that symbiogenesis—the formation of new species through symbiotic mergers—was a major mechanism of evolutionary innovation7 .
This perspective has gained new relevance with recent research into the human microbiome6 .
- Lynn Margulis6
Lynn Margulis left an indelible mark on biology, fundamentally transforming our understanding of life's history and interconnectedness.
Her work replaced a narrative of relentless competition with a more nuanced view that recognized cooperation as a creative force in evolution. By demonstrating that complex cells emerged through symbiotic mergers, she provided a scientific basis for understanding life as fundamentally collaborative—a vision with profound implications for how we see ourselves and our relationship to the natural world.
The journey from dismissed heretic to celebrated scientific hero stands as a testament to her persistence, intellectual courage, and unwavering commitment to evidence. This integrity, combined with her revolutionary insights, cemented her place as one of the most important biologists of the 20th century—one whose vision of a "symbiotic planet" continues to inspire new generations of scientists to see the living world as deeply interconnected and collaborative.