Part One: The Woman Who Refused to Look Away

In 1953, a fifteen-year-old girl named Lynn Alexander enrolled at the University of Chicago, already too impatient for ordinary schooling. When she encountered genetics, something clicked: the cell, as she began to see, was not a simple bag of molecules or even a machine; it was a world. Four years later, at age 19, she earned a BA from the University of Chicago in Liberal Arts. She was born to be a woman scientist: curious, bold, dedicated, independent, and ambitious. However, she was a product of her time. Right after graduation, she married the astronomer, Carl Sagan, who later became the face of U.S. space program and a star science communicator.

We might imagine that two super smart persons, living together, would have fun and amazing lifestyle. However, a house was too small for two genii.  The union lasted until 1964 — Sagan expected a traditional wife, and Lynn was simultaneously nursing two infants, pursuing a doctorate, and holding together an intellectual life his ego barely had room for. She quitted to be a wife for pursuing a scientific career, so she can keep asking a question lingering in her sharp mind: why did mitochondria look so much like bacteria?

Scientists had noticed the resemblance since mitochondria were first described in the late nineteenth century and had filed it away as a curiosity. Margulis could not file it away. Then, in a seminar, a professor showed her DNA inside chloroplasts — and everything became suddenly, violently clear. She was not surprised; of course there was DNA in there. If chloroplasts had once been free-living photosynthetic bacteria — swallowed by a larger cell and gradually enslaved over hundreds of millions of years — then they would still carry their own genome, locked inside their host like a message in a bottle. She came with this bold hypothesis: the eukaryotic cell was not an individual. Instead, it was a confederation of ancient bacteria that had stopped fighting with the predatory host and started cooperating.

She spent the late 1960s building her case and submitted her synthesis to journal after journal, and it was rejected by fifteen journals rejected it. A grant proposal came back annotated: Your research is crap. She simply sent it out again. Finally, the Journal of Theoretical Biology published "On the Origin of Mitosing Cells" in 1967. Initially, the scientific community received it with skepticism and contempt. In the early 1980s, biochemists sequencing mitochondrial DNA found it strikingly similar to bacterial DNA and dramatically different from the cell's nuclear genome. The long argument was simply over; Margulis had won the case.

Part Two: The Man Who Invented the Lens

Several hundred miles away, at the University of Illinois, a quietly obsessive man was asking a question no one had yet figured out how to ask. Carl Woese had come to microbiology not through conventional biology training - a Yale doctorate in biophysics, and years at General Electric's research laboratory. When he joined the Illinois faculty in 1964, he brought the habits of a physicist: a taste for quantitative measurement, rather than observation with subjective opinion. He looked at evolutionary biology and saw a field flying blind. It could describe the history of life in broad strokes but not measure it. More specifically, how to evaluate the relation between different life forms quantitatively?

In 1965, he read a paper proposing that macromolecule sequences were "documents of evolutionary history" —  the differences in sequences of two species must be originated from variation of the earlier version over time, therefore form the lineage records. He thought for months about which molecule to choose — it had to be present in every organism, ancient, and slowly enough evolving to be compared across billions of years. The answer, he realized, had been sitting inside every living cell all along: ribosomal RNA, the core of the protein-building machinery, conserved so deeply that even organisms separated by two billion years of evolution still carried recognizable versions of it.

The method he developed was slow and radioactive. Woese and his postdoctoral fellow, George Fox, would grow bacteria spiked with radioactive phosphorus, extract the ribosomal RNA, cut it into fragments, separate those fragments on a gel, and press photographic paper against the gel for days until the radioactive bands imprinted their pattern onto the big X-ray film. The black bands on the grayish, semi-transparent background were the signature note of each organism. Woese studied these autoradiographs on a light table for hours, reading each band like a word in a language he was still learning.

One evening in 1976, Fox brought him a fresh autoradiograph from a methanogen — a microbe that lived in oxygen-free environments and exhaled methane. Woese held it up to the light and looked at the banding pattern. He looked again. Its pattern did not match bacteria or eukaryotes. Not anything in the growing library of patterns his laboratory had accumulated over years of work. Whatever this organism was, it was not a variant of a known form of life. It was a different kind of life entirely.

He set the autoradiograph down on the light table and stood very still.

"George," he said quietly. "This creature is not a bacterium."

In 1977, Woese and Fox published their findings. The New York Times ran the story on its front page. Woese found himself briefly famous — and then furiously attacked. The Nobel laureate Salvador Luria told Woese's colleague Ralph Wolfe to dissociate himself from this "nonsense" to protect his reputation. Ernst Mayr, the greatest evolutionary biologist of the century, dismissed the three-domain concept entirely — a position he held until his death in 2005. Woese, a profound introvert who left his mail unopened for months and retreated from confrontation, was wounded to his core. A Science profile in 1997 called him "Microbiology's Scarred Revolutionary." But genomic sequencing confirmed everything the autoradiographs had shown. By 1990, Woese formally proposed the three-domain system — Bacteria, Archaea, and Eukarya — now standard in every biology textbook on Earth.

Part Three: Allies, Rivals, Different Music

The worlds of Margulis and Woese converged in the 1970s — fruitfully, then acrimoniously. Woese's molecular tools confirmed that chloroplast DNA was cyanobacterial in origin, exactly as Margulis had proposed. His chronometer gave endosymbiosis its firmest foundation. In this sense they were allies.

But a deep philosophical disagreement divided them. Margulis championed the five-kingdom classification, arguing that the fundamental boundary in biology was between prokaryotes and eukaryotes — the divide between organisms that had undergone symbiogenesis and those that had not. Woese's three-domain system crossed that boundary, elevating the Archaea to a domain equal to the others, splitting the prokaryotes based on molecular sequence data alone. In Symbiotic Planet, Margulis wrote that his scheme "obscures rather than illuminates the critical distinction between prokaryotes and eukaryotes." Woese found her position a failure to follow evidence wherever it led. He was reportedly as wounded by her opposition as by Mayr's.

The gulf was philosophical. Margulis saw the cell as the primary unit of evolutionary drama. Woese saw the molecule as the primary witness. Both were pursuing truth. They were using different instruments and hearing different music.

Part Four: The Caterpillar and the Mirror

To understand Margulis fully, one must spend a moment with a caterpillar.

In 2009, Donald Williamson, an eighty-seven-year-old retired zoologist, proposed that the butterfly life cycle was the product of an ancient hybridization — the accidental mating of an ancestral insect with a velvet worm. The caterpillar was the velvet worm's contribution; the winged adult the insect lineage's. Harvard's Gonzalo Giribet called it "the most stupid thing that has ever been proposed." The person who got it published in PNAS was Lynn Margulis.

As a National Academy member, she had access to PNAS's "communicated submission" route — Track I — in which a member could sponsor a paper, select peer reviewers herself, and deliver the manuscript with those reviews already in hand. She later admitted to a Scientific American reporter that she had sought "6 or 7" reviews to accumulate the "2 or 3" positive ones required for acceptance. The PNAS editor-in-chief Randy Schekman wrote demanding a satisfactory explanation for her "apparent selective communication of reviews." The formal rebuttal appeared in the same journal under the stark title "Caterpillars did not evolve from onychophorans by hybridogenesis." Within months, PNAS eliminated the communicated submission track entirely, effective July 1, 2010.

The episode illuminates the precise mechanism that made Margulis both great and, in certain chambers, destructive. The conviction that had driven her through rejections with endosymbiosis —that a scientist who could see further had an obligation to push past institutional gatekeeping — was identical in structure to the conviction that led her to shop for favorable reviewers for Williamson. In her own mind the situations were the same: heterodox idea, hostile mainstream, determined advocate. Her consistent fighting spirit blindsided her. In the 1960s, she identified the evidence rejected by the conventional wisdom. By 2009, it was the evidence that was against Williamson.

In her final Discover interview, shortly before her death in November 2011, Margulis said: "I don't consider my ideas controversial. I consider them right." It was the purest expression of who she was — and of the collapse, somewhere along the way, of the distinction between controversial and right that had been, simultaneously, her greatest strength and her fatal flaw.

Part Five: Two Personalities, One Legacy

Margulis and Woese survived institutional hostility by opposite strategies. Margulis attacked — outspoken, combative, fighting critics in print, writing popular books with her son Dorion Sagan. Woese retreated — reclusive, private, returning always to his data. His wife discovered, buried in months of unopened mail, a letter informing him he had won the Leeuwenhoek Medal, microbiology's highest honor: the man who had remade the tree of life, too wounded by years of rejection to believe the world might have finally written to say he was right. Where her wound expressed itself as aggression, his expressed itself as a quiet, permanent melancholy that the honors — MacArthur Fellowship, National Medal of Science, the Crafoord Prize — never entirely lifted. He died of pancreatic cancer in December 2012, never having won the Nobel Prize.

Their philosophies were mirror images. Margulis saw evolution as fundamentally cooperative — life advancing through merger and mutual dependence, not ruthless competition. "Life did not take over the globe by combat, but by networking." Woese, working from the molecule outward, saw evolution as a process legible only through deep time and sequence — a story written in RNA before any organism was large enough to see. Together they described the same history from opposite ends: she from the cell looking inward at its bacterial passengers, he from the molecule looking outward at the branching tree of all life.

Epilogue: Shark Bay, April 2026

On the western coast of Australia, in a hypersaline bay called Gathaagudu — Shark Bay — there are mats of microbes living on the floor of sunlit tidal pools that look, to the naked eye, like nothing more than dark, slightly slimy rock. They are stromatolites, and their ancestors built the same structures more than three billion years ago, before animals existed, before plants existed, before anything with a nucleus had appeared on Earth. They are the oldest neighborhood still occupied — the living remnant of the world that Margulis and Woese spent their lives trying to understand.

In April 2026, a multidisciplinary team led by Brendan Burns, Debnath Ghosal, Iain Duggin, and Kate Michie at University of New South Wales, Australia, published a paper in Current Biology (https://www.sciencedirect.com/science/article/pii/S0960982226003301) that reads, to anyone familiar with the previous sixty years of biology, like the closing chapter of a story begun in a Berkeley seminar room and a third-floor laboratory in Illinois. The paper described the cultivation — four to five years in the making — of a novel Asgard archaeon recovered from the subsurface layers of those Shark Bay microbial mats. They named it Nerearchaeum marumarumayae: the genus from Nereus, the ancient Greek god of the deep sea; the species from marumarumayae, a word in the language of the Malgana people, the traditional custodians of Shark Bay, meaning "ancient home."

The Asgard archaea — a group first identified from environmental DNA sequences in 2015 — are considered the closest living prokaryotic relatives of eukaryotes. They carry, encoded in their genomes, a remarkable collection of proteins previously thought to be exclusively eukaryotic: proteins shaping membranes, proteins organizing the cytoskeleton, the molecular blueprints for cellular complexity. The implication had been building for a decade: eukaryotes had not invented these features from scratch. They had inherited them from an Asgard archaeal ancestor that was already, in some pre-eukaryotic sense, becoming complex — and that had then entered a fateful partnership with a bacterium. That bacterium became the mitochondrion. That partnership became every complex cell on Earth.

Using electron cryo-tomography — an imaging technique producing three-dimensional portraits of cells at nanometer resolution — the Shark Bay team saw something no scientist had seen before: Nerearchaeum marumarumayae and its bacterial companion Stromatodesulfovibrio nilemahensis physically connected by fine nanotube-like structures threading between their bodies. "This could be a little model for how these kinds of partnerships started," said the principal investigator Brendan Burns, "and ultimately formed eukaryotes."

In those nanotubes, the legacies of Margulis and Woese converge more completely than they ever did in life.

Margulis's vision — that the eukaryotic cell was born from symbiotic merger, that life's greatest leap was taken not by a single organism but by two organisms learning to live inside each other — is confirmed here at a resolution she could never have imagined. The Asgard archaea are the answer to the question her studies always implied but could never fully answer: who was the ancestral host that absorbed that ancient bacterium? Woese's contribution runs just as deep, if less visibly. The Asgard archaea were found in the first place through metagenomics — the sequencing of environmental DNA without culturing organisms in the lab. That technique rests entirely on the framework Woese built: the ribosomal RNA sequences he spent a decade reading from radioactive autoradiographs in Urbana are the same molecular markers that metagenomicists now use to survey thousands of species from a tablespoon of ocean sediment.

They could not agree, in life, about how to classify the Archaea. They would likely have disagreed about how to interpret this paper. But the nanotubes connecting archaeon to bacterium in the laminated mats of Shark Bay do not care about either argument. They are doing what the ancestors of every eukaryote on Earth once did: reaching across the divide between two kinds of life, touching, negotiating, beginning the slow process of becoming one.

The microbes are still at it. Two billion years on, in a sunlit bay in Western Australia, the story that Margulis and Woese each half-told is still unfolding — patient, microscopic, and indifferent to the question of who deserves the credit.

 Author's note: The writing of this article was assisted by Claude with the following prompt: 

1. Write a story about Lynn Margulis and Carl Woese by the following plot: (1) What triggered Margulis to develop her theory of eukaryotic cells originated from symbiosis; (2) what triggered Woese to develop his theory of three kingdoms of lives; (3) what kind of opposition they encountered, how they overcome it and how their theories were accepted, recognized, and eventually celebrated by biologists; (4) how their theories agree and disagree with each other, and how they thought about each other's theory; what are the philosophy behind their concepts; (5) how their personality impacted their career path and family life; (6) how people consider their legacy and their legends.
2. Reorganize the article to use the "scandal of hybrid origin of butterfly" to illustrate Margulis' personality, and analyze how this reflected the difficulties in her career path.
3. What were the eureka moments in the stories of Margulis and Woese? Revise the story to make these moments more dramatic to impress readers.
4. Add a part to describe how Margulis' and Woese's research legacy lead to this recent paper, An Asgard archaeon from a modern analog of ancient microbial mats (Current Biology [Volume 36, Issue 8](https://www.sciencedirect.com/journal/current-biology/vol/36/issue/8), 20 April 2026, Pages 2090-2103.e7), as the ending of this story.
5. Shorten the whole story to less than 3000 words.