THE SECRET OF CELLS

You are not an individual. You are an arrangement.
Every cell in your body contains the descendants of bacteria that were swallowed roughly two billion years ago and never digested. They still carry their own DNA. They still divide on their own schedule. They are, by every reasonable measure, guests who have overstayed by a margin no landlord could tolerate, and without them you could not stand up.
The woman who insisted on this was named Lynn Margulis, and for two decades she was the least comfortable person in American biology. She was twenty-eight when she wrote the paper. It was rejected roughly fifteen times. When it finally appeared, the discipline responded with a silence so complete that colleagues advised her, kindly, to work on something else. She did not. By the time she died in 2011 her heresy was on page one of every cell biology textbook in the world, and she had moved on to fights she could not win, some of which she should never have started.
This book tells her story and follows her question further than she took it. If a cell can be a merger, what else is one? Lichens turned out to be committees. Termites digest wood by subcontracting. A quarter of your body weight, roughly, is not you. Somewhere in the Pacific there is a plankton cell in the act of swallowing something right now, and biologists are watching, because for the first time the merger is happening on a timescale a career can accommodate.
Along the way it takes up the harder problem underneath: where one living thing ends and another begins, and why the answer has always been decided by committee rather than discovered. It argues, with a formal apparatus kept firmly out of sight, that cooperation is not the exception biology has to explain away but the state a system settles into when nothing is pushing it apart. And it looks squarely at the last decade of Margulis's life, when the same talent that let her step outside one orthodoxy led her straight into positions that were simply wrong, because a mind that cannot be trapped by a frame has no built-in instinct for which way to jump.
A book about the deepest merger in the history of life, and about the difficult, funny, impossible woman who would not let anyone forget it.
Keywords: evolution, symbiosis, cell biology, history of science, microbiology, scientific controversy, origins of life