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An engaging history reveals the scientific struggle to understand horizontal gene transfer

The Tangled Tree: A Radical New History of Life

David Quammen
Simon & Schuster
487 pp.
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Eight percent of the human genome originated in virus genomes, including genes now essential to human life. This is just one insight gleaned from the current deluge of genome data that is providing ever more evidence for what we have long known to be true about microorganisms: The transfer of genetic material from one organism to another, or horizontal gene transfer, is an important source of variation and a factor driving evolution.

In David Quammen’s new page turner, The Tangled Tree: A Radical New History of Life, the author reveals how new molecular techniques have come to revolutionize the way we understand evolutionary processes and how we classify life into coherent groups. In an accessible style that has won him accolades in the past, Quammen does a marvelous job of weaving together the scientific and human story of this revolution.

In the first chapters, Quammen lays the groundwork, recounting how a tree came to be the preferred graphic illustrating order in the complexity of life. Here, he includes anecdotes about the historical figures involved and colorful descriptions of their trees. The geologist Edward Hitchcock’s tree, for example, is described as looking “more like a windbreak of tightly placed Lombardy poplars grown to maturity along a roadway.”

Early in the book, Quammen introduces Carl Woese, the pioneering scientist who used ribosomal RNA differences among microorganisms to discover a third kingdom of life (Archaea). Quammen meticulously researched Woese’s life, conducting countless interviews with those who knew him and poring over his papers in the archives at the University of Illinois. He provides a particularly detailed account of the development of Woese’s famous 1980 paper with George Fox that described the evidence for three kingdoms (1), even delving into the contentious discussion of authorship order among the two.

The stories of other well-known scientists weave in and out, including Lynn Margulis, with whom Woese battled bitterly over whether there are five or three kingdoms of life. We learn that, ironically, it was Woese’s ribosomal RNA evidence that showed bacteria to be the ancestor of mitochondria in eukaryotes, consistent with Margulis’s once controversial endosymbiotic theory.

The primary evidence for horizontal gene transfer, the reason for the tangles in the tree, comes from comparative molecular analysis. Here again, Quammen uses the stories of scientists to contextualize the technical explanations of bacterial gene transfer mechanisms, describing the exciting discoveries of Oswald Avery, Frederick Griffith, Tsutomu Watanabe, and Esther and Joshua Lederberg.

Like Quammen’s previous works, this book is meant to be widely read and communicates the process of scientific inquiry as effectively as it does the results of the inquiry. The bitterness and grudges that existed between scientists passionately competing in the discovery process are described along with the selfless gestures and lifelong loyalties that often existed in the same relationships. On occasion, Quammen takes the reader aside to provide a direct insight, such as the fact that relationships among scientists are always shaped by personal chemistry: “It’s a smallish world these scientists live in, much interconnected.”

My only criticism is that some of the book’s shorter sections strayed into topics that seemed a bit out of place for a primarily historical account. For example, there is a short section on CRISPR that did not seem especially relevant to the book’s central themes. This, however, is a minor concern. Such diversions certainly did not detract from the overall reading experience.

In The Tangled Tree, David Quammen has once again crafted a delightful read on a complex and important subject. This story about the revolution in our understanding of the history of life is a tale well told—and one that has far-reaching implications.

About the author

The reviewer is at the Department of Biology, Behrend College, Pennsylvania State University, Erie, PA, USA.