The scientific luminary Lynn Margulis, an outspoken pioneer in evolutionary biology, died on 24th November, in Amherst, Massachusetts, aged 73. Renowned for a radical theory of the origin of complex cells, her death marks the loss of a unique and contrarian voice in biology, and the closing of a vibrant and spirited life.

I was fortunate to meet Prof. Margulis in Oxford last year, in an impromptu and surprising encounter. “Is that… the Lynn Margulis,” a friend had said, peering incredulously at a seminar listings noticeboard, “Why has nobody told us about this?” Ten minutes of frantic sprinting later, we slipped into a seminar room on South Parks Road. The audience numbered roughly six.

“You’re here for Lynn?” somebody asked warmly, and then added, “We’ll have to wait a second or two. We know she’s here somewhere, but the thing about Lynn is she keeps you guessing.”

Lynn Margulis has had people guessing for decades. Her provocative hypotheses – generated at almost improbable rates – have engrossed and outraged the scientific establishment for forty years. She brought to evolutionary biology the expansive, daringly playful imagination of a poet or playwright, unafraid to dream up eccentric and spirited plots for a cast of outlandish characters, and ask nature, puckishly, if it had had similar thoughts. It is a testament to her scientific intuition that some of the time it had.

Margulian endosymbiosis, as it is known, remains one of the most beguilingly wonderful ideas in modern science, and its eponymous discoverer deserves a place amongst the pantheon of scientific pioneers. At the cellular level, eukaryotic life – essentially everything besides bacteria and viruses – has long entranced biologists: in all its sublime complexity, the eukaryotic cell has an aura of extraordinary mystique. It shimmers with a bewitching intricacy, an elaborate biomolecular marionette fashioned by aeons of evolutionary ingenuity. Margulis’s astonishing vision lay in seeing that this integrated whole, the quintessence of biological cohesion, had its origins in disparate, independent, elemental entities, joined in a marriage of convenience somewhere in the meandering backwaters of deep time. In essence, a bacterium found itself inside a larger cell, and, remarkably, stayed for posterity. Its descendants are within us all today; indeed, they part of us. We are, in a spectacular sense, part bacterial.

Audaciously resuscitating an obscure and maligned tradition stretching back to the 1880s, Margulis’s insight was a virtuoso and rebellious move, but also – it was felt at the time – an outrageous affront to biological sanity. Across the subsequent decades, she acquired a contrarian reputation, and came to see herself as a dissident voice in a science contaminated by ideological convictions. She was apt to dismiss canonical neo-Darwinian results as crude, capitalist misreadings of evolutionary history; for her, biology’s ongoing love-affair with microeconomics was a disturbing and unsustainable fling, dangerously one-dimensional and inevitably destined to self-combust.

Her instinctive aversion to the Machiavellian mood of modern biology, then, grew from a sense that cooperation in nature was a ubiquitous and powerful driver of innovation, and she did not shy from offering broad cultural diagnoses for her colleagues’ obstinacy: their commitment to monophyly (having a single ancestor) was nothing more than the latent misfiring of monotheistic and monarchical inclinations, and the resistance to accepting symbiosis as a driving force for evolutionary novelty grew from a fear of its “female” connotations. The world as she saw it cannot be meaningfully fragmented, and she warmed naturally and famously to Lovelock’s Gaia hypothesis: the Earth is a vast and indissoluble community, immune to the atomising tendency of “feudal” science.

Margulis was admitted to the University of Chicago aged 14, after a difficult childhood under insensitive parents. Two years later, she fell in love with Carl Sagan, whom she married before the age of 20. She found in biology a quiet, contemplative, aesthetic privacy, seeing “solitude” as vital for the scientific worker. She divorced twice, later remarking that, when juggling marriage, science, and her children, “something has to go”. Despite her famed anti-establishment views, her awards and positions were legion, and included the coveted Darwin-Wallace Medal and America’s National Medal of Science.

Looking back, there was a certain pregnant poignancy about that little lecture room on that quiet summer afternoon. Margulis’s shameless enthusiasm, her insatiable curiosity – “I hear you have very good algae in Oxford; when can I go searching?” – as well as her passion for the smallest of animals, now strike a painful note. With her distinctive, faintly gravelled voice, she spoke earnestly and excitedly about her future projects, and, in the brief conversation we were lucky to have afterwards, she chatted with an affable, effervescent energy that inspired us all.

Charles Darwin once remarked that anyone “who dares to waste one hour of time has not discovered the value of life”. Lynn Margulis was an astonishing and visionary figure, with an insatiable appetite for knowledge. I believe – and I don’t think I’m alone – that Darwin and her would have got on like a house on fire.

She is survived by her four children.