The Tangled Tree: A Radical New History of Life. David Quammen

brought radical changes—to his own field, to the story of life—and yet he remains unknown to most people outside the rarefied corridors of molecular biology.

      Carl Woese was a complicated man—fiercely dedicated and very private—who seized upon deep questions, cobbled together ingenious techniques to pursue those questions, flouted some of the rules of scientific decorum, made enemies, ignored niceties, said what he thought, focused obsessively on his own research program to the exclusion of most other concerns, and turned up at least one or two discoveries that shook the pillars of biological thought. To his close friends, he was an easy, funny guy; caustic but wry, with a love for jazz, a taste for beer and scotch, and an amateurish facility on piano. To his grad students and postdoctoral fellows and laboratory assistants, most of them, he was a good boss and an inspirational mentor, sometimes (but not always) generous, wise, and caring.

      As a teacher in the narrower sense—a professor of microbiology at the University of Illinois—he was almost nonexistent as far as undergraduates were concerned. He didn’t stand before large banks of eager, clueless students, patiently explaining the ABCs of bacteria. Lecturing wasn’t his strength, or his interest, and he lacked eloquent forcefulness even when presenting his work at scientific meetings. He didn’t like meetings. He didn’t like travel. He didn’t create a joyous, collegial culture within his lab, hosting seminars and Christmas parties to be captured in group photos, as many senior scientists do. He had his chosen young friends, and some of them remember good times, laughter, beery barbecues at the Woese home, just a short walk from the university campus. But those friends were the select few who, somehow, by charm or by luck, had gotten through his shell.

      In later years, as he grew more widely acclaimed, receiving honors of all kinds short of the Nobel Prize, Woese seems also to have grown bitter. He considered himself an outsider. He was elected to the National Academy of Sciences, an august body, but tardily, at age sixty, and the delay annoyed him. He became, by some reports, distant from his family—a wife and two children, seldom mentioned in published accounts of his scientific labors. He was a brilliant crank, and his work triggered a drastic revision of one of the most basic concepts in biology: the idea of the tree of life, the great arboreal image of relatedness and diversification. For that reason, Woese’s moment of triumph in Urbana, on November 3, 1977, has its place near the core of this book.

      Other scientists and other discoveries are connected to Woese and his tree. A little-known British physician named Fred Griffith, for instance, in the mid-1920s, while researching pneumonia for the Ministry of Health, noticed an unexpected transformation among bacteria: one strain changing suddenly into another strain, presto, from harmless to deadly virulent. This was important in terms of public health (bacterial pneumonia was in those days a leading cause of death) but also, as even Griffith didn’t realize, a clue to deeper truths in pure science.

      The mechanism of Griffith’s perplexing transformation remained obscure until 1944, when a quiet, fastidious researcher named Oswald Avery, at the Rockefeller Institute in New York, identified the substance, the “transforming principle,” that can cause such sudden change from one bacterial identity to another. It was deoxyribonucleic acid. DNA. Less than a decade later, Joshua Lederberg and his colleagues showed that this sort of transformation, relabeled “infective heredity,” is a routine and important process in bacteria—and, as later work would show, not just in bacteria. Meanwhile, the corn geneticist Barbara McClintock, discovering genes that bounce from one point to another on the chromosomes of her favorite plant, worked with very little support or recognition through the prime years of her career—and then accepted a Nobel Prize at age eighty-one.

      Lynn Margulis, a Chicago-educated microbiologist unique in almost every way, shared at least one thing with McClintock: the frustrations of being dismissed by some colleagues as an eccentric and obdurate woman. In Margulis’s case, it was for reviving an old idea that had long been considered wacky: endosymbiosis. What she meant by the term was, roughly, the cooperative integration of living creatures within living creatures. That is, not just tiny creatures within the bellies or noses of big creatures, but cells within cells. More specifically, Margulis argued that the cells constituting every creature in the more complex divisions of life—every human, every animal, every plant, every fungus—are chimerical things, assembled with captured bacteria inside nonbacterial receptacles. Those particular bacteria, over vast stretches of time, have become transmogrified into cellular organs. Imagine an oyster, transplanted into a cow, that becomes a functional bovine kidney. This seemed crazy when Margulis proposed it in 1967. But she was right about the matter, mostly.

      Fred Sanger, Francis Crick, Linus Pauling, Tsutomu Watanabe, and other scientists played crucial parts in this chain of events too, sometimes by force of personality as well as by scientific brilliance. Slightly deeper in the past lie obscure figures such as Ferdinand Cohn, Edward Hitchcock, and Augustin Augier, as well as more famous ones, including Ernst Haeckel, August Weismann, and Carl Linnaeus. The ghost of Jean-Baptiste Lamarck rises here again to skulk along inescapably in the shadows of evolutionary thinking.

      Such people, all contributors to a scientific upheaval, are of additional interest for the ways their works grew from their lives. They serve as good reminders that science itself, however precise and objective, is a human activity. It’s a way of wondering as well as a way of knowing. It’s a process, not a body of facts or laws. Like music, like poetry, like baseball, like grandmaster chess, it’s something gloriously imperfect that people do. The smudgy fingerprints of our humanness are all over it.

      Humans aren’t the only important characters in this book. There are also a lot of other living creatures, whose unique histories and foibles illustrate points in the story I’m trying to tell. Many of them are microbes—those bacteria I’ve mentioned, those archaea, and other teeny things. Please don’t be fooled by their smallness; their implications and impacts are big. And don’t be daunted by their names, which are mostly expressed in scientific Latin: Bacillus subtilis and Salmonella typhimurium and Methanobacterium ruminantium and other monstrous tongue twisters. The reason I call them by those names is not because I like arcane language but because no other labels exist. Microbes generally don’t get the courtesy of common names at the species level, casual monikers such as southern giraffe, olive bunting, monarch butterfly, and Komodo dragon. If the bacterium known as Haemophilus influenzae could be accurately called Fleming’s nose-tickler, I promise you I would do it.

      One other featured character, of the human sort, should be introduced here. He’s a bearded American microbiologist with a penchant for philosophical musing, tucked away at a university in Nova Scotia. This man has linked Carl Woese, Lynn Margulis, and much of the new work in molecular phylogenetics into a pungent challenge against biology’s central metaphor. His name is Ford Doolittle. He’s tall, diffident in manner though not in thought, and enjoys causing a little intellectual discomfort. At the turn of the millennium, Doolittle published an essay titled “Uprooting the Tree of Life,” which helped release a cascade of arguments. I caught wind of him through that essay and his related writings, notably those in which he discussed horizontal gene transfer and its implications. “Horizontal what?” was my earliest thought. Then I pilgrimed to Halifax and camped for days in his office. Doolittle is semiretired, still guiding graduate students, still well funded with a prestigious research grant, but no longer growing radioactive bacteria in a lab in order to deduce bits of their genomes (the totality of their DNA) from images on chest X-ray films. He’s no longer pulling chopped molecules through electrophoretic gels, as he did in the pioneer days. He reads, he thinks, he writes, he draws. (He takes art photographs, mainly for his own amusement, and occasionally mounts a gallery show, but that’s another realm of enterprise entirely.) In fact, part of what has made Ford Doolittle so influential is that, in addition to his qualifications in biology, he writes far better than most scientists—and he draws deftly, turning big concepts into graceful, cartoony shapes. Doolittle’s father was a painter and an art professor. Young Ford considered an art career himself, though his father called that “a terrible way to make a living.” Then, when he was fifteen years old, in 1957, the Soviets put Sputnik into space, persuading Ford and many other Americans that science and engineering were the more urgent, forceful pursuits. He went to Harvard College and studied biochemistry. The artistic impulse never left him. Nowadays, to illustrate his subversive thinking and his genial