The Tangled Tree

450 pages

Life is complicated. More than a century after Charles Darwin formulated his theory of evolution, science’s insights into how organisms — including ourselves — came to be and how they have changed over time reveal a living world far more complex, and stranger, than Darwin could have ever imagined. Just 40 years ago, for example, a scientist named Carl Woese discovered an entirely new category of life. Known as archaea, these primordial microbes are now thought to be the building blocks of life that gave rise to our earliest ancestors, as well as other animals, plants, and fungi. The tree of life, it turns out, has more branches — and roots — than we thought.

In The Tangled Tree: A Radical New History of Life, veteran science journalist and author David Quammen chronicles the paradigm-shifting developments in biology that have upended our understanding of life on Earth, from early evolutionist Jean-Baptiste Lamarck’s flawed but prescient 1809 diagram of animal diversity to the intricate new tree of life unveiled in the scientific journal Nature in 2016 and the cutting-edge science of gene editing.

“What happened, over the course of roughly four billion years, to bring life from its primordial origins into the fluorescence of diversity and complexity we see now?” Quammen writes in the book’s introduction. “How did it happen? By what concatenation of accident and determination did it yield creatures so wondrous as humans — and blue whales, and tyrannosaurs, and giant sequoias?”

Through the trials and triumphs of the scientists who labored to unearth the answers to these questions, we learn how the tree of life grew over the centuries, sprouting new branches and new roots, and how the brave new world of modern molecular biology is yielding an ever more granular view of life’s scaffolding and mechanics. In recent years, Quammen notes, scientists have discovered that genetic information can be passed from one species to another — via infection, for example — in a phenomenon known as “horizontal gene transfer,” in addition to the usual path of heredity. And we learn how the sequencing of the human genome — identifying all the bits and pieces that compose our DNA blueprint and their order — has allowed scientists to parse which genes control which traits and “edit” them, potentially leading to new ways to treat diseases.

Unpacking more than two centuries of biological research is a massive undertaking — it took four years for Quammen to research and write the book — but his talent for weaving a good yarn out of complex research and the scientific process, along with his distinctive wit and crystalline writing, ensures that The Tangled Tree never becomes a tangled mess. In chronicling how scientists sequenced the human genome in the early 2000s, he notes that a little-known aspect of the discovery was that it revealed a “vast amount of seemingly pointless repetition,” as he puts it. “There it sat, within the genome, like a mammoth landfill of what had been called ‘junk DNA,’ ” he writes. “So much redundant blather in the fundamental human blueprint seemed almost embarrassing.” Yet those repetitive sequences turned out to be important clues to how humans evolved.

In Quammen’s hands, scientific discovery comes alive as the messy, difficult, sometimes frustrating, sometimes joyous, and fundamentally human pursuit that it is. Scientists, he reminds us, are just as complicated as the rest of us. In his recounting of Woese’s discovery of the archaea, for example, Quammen shows us the man as well as the work, and how personality and relationships can shape science. Described by one colleague as “complex” and sometimes obstinate, Woese, we learn, also had a well-developed sense of mischief. Entomologist Charlie Vossbrinck, the late Woese’s former University of Illinois colleague and friend, recalls how the two would ferment their own champagne, using champagne yeast from the school’s microbiology department. “At the end of two weeks it would be pee yellow, you know, and, on a Friday afternoon, me and Carl would start drinking it,” Vossbrinck tells Quammen. Quammen adds: “The more they drank, the better their homemade concoction seemed.”

Some of the most engrossing passages in the book recount the surprising ways that scientists arrived at their hard-won, groundbreaking insights. A pivotal discovery in genetics decades before the sequencing the human genome came from what at first glance seems like a simple corn-growing experiment. In the 1940s, plant geneticist Barbara McClintock planted various types of maize on an acre of land at Cold Spring Harbor Laboratory on Long Island and crosspollinated them by hand. She forced mutations by X-raying the kernels; the mutations showed up as different colors. McClintock found that certain mutations seemed to affect how genes are expressed, and that genes can jump from one part of the genome to another. These were major achievements, but it took decades for the science community to fully appreciate the importance of her discoveries. Finally, 40 years later, she won a Nobel Prize.

The Tangled Tree achieves what many science writers aspire to but rarely manage to pull off: an entertaining, relatable, and deeply informative exploration of a complex subject that even someone with only a casual interest in science would find difficult to put down. — April Reese

April Reese is a freelance science and environment writer and editor based in Santa Fe. Her work has appeared in publications that include Smithsonian .com, Science magazine, National Geographic News, Discover, bioGraphic, The Christian Science Monitor, and The Atlantic online.