"The 'tree of life' that we have believed in as the picture of evolutionary history, ever since Darwin, is not entirely wrong but drastically incomplete and too simple. Tree branches always diverge, and it turns out evolutionary lineages diverge and converge. So limbs grow together and there are channels that have moved from one branch to another. The premise of my book is that the tree of life is not strictly a tree—it is a web, it’s a network, it’s something for which we don’t have a visual metaphor. It’s a tangled tree and the history of life is radically different from what we thought we knew 45-50 years ago. . ." -- David Quammen
The following highlights are from a conversation with David Quammen about his book, The Tangled Tree: A Radical New History of Life. To hear the full conversation, click the link above or subscribe to our podcast.
Sarah Aronson: In the terms of your book, what are you made of?
David Quammen: I, like all other humans, am made of DNA that has descended straight down for millions and millions and millions of years through the animal lineage; some bacterial DNA that got into the lineage of complex cells about 2 billion years ago; and I am 8% virus. Like all other humans, my genome contains 8% DNA captured from retroviruses that have infected the animal lineage over the last hundred million years or so, and because those viruses infected reproductive cells, they became part of animal heritage, allowing us to become mammals, allowing us to become humans.
In the simplest language possible, can you describe the premise of your book?
The premise of the book is that the “tree of life” that we have believed in as the picture of evolutionary history, ever since Darwin, is not entirely wrong but drastically incomplete and too simple. Tree branches always diverge, and it turns out evolutionary lineages diverge and converge. So limbs grow together and there are channels that have moved from one branch to another. The premise of my book is that the tree of life is not strictly a tree—it is a web, it’s a network, it’s something for which we don’t have a visual metaphor. It’s a tangled tree and the history of life is radically different from what we thought we knew 45-50 years ago because of discoveries that were made from gene sequencing led by a little man with white hair in Urbana, IL named Carl Woese.
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You write, “Scientific relationships are always shaped by personal chemistry as well as by work and ideas.” What did you learn about the about the scientific community overall?
Science is a human process and it involves ideas, evidence, argument, and hypothesis testing. It also involves drinking beer, and conversations in hotel corridors, and cliques, loyalty and disloyalty, and competition—a lot of competition in science, and backstabbing, and selflessness, and ego. All those things. Science is a human process just the way baseball, and Gregorian chant, and Grandmaster chess are human activities. It’s got our smudgy fingerprints all over it. It’s got humanity all over it.
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I want to try and get the three main points down for listeners:
- There is a blurring of lines between species;
- We are not individuals, we are mosaics;
- Inheritance does not flow vertically, it can flow horizontally.
Perfect! Those are I what I call, near the end of the book, the three categoricals. Three categorical ideas that we have embraced for a century and a half, since Charles Darwin published “The Origin of Species.”
1) That species are discrete entities somehow standing separate in time and space;
2) That an individual is a discrete unit: there’s an individual named Charles Robert Darwin, there’s an individual named Sarah Aronson, there’s an individual dog named Steve;
3) That the history of life is shaped like a tree.
And as I say, those three categoricals, turns out they’re all wrong. They’re not completely wrong, but they’re partially wrong in really important ways that I try and illuminate for people by telling human stories in this book.
About the Book:
Nonpareil science writer David Quammen explains how recent discoveries in molecular biology can change our understanding of evolution and life’s history, with powerful implications for human health and even our own human nature.
In the mid-1970s, scientists began using DNA sequences to reexamine the history of all life. Perhaps the most startling discovery to come out of this new field—the study of life’s diversity and relatedness at the molecular level—is horizontal gene transfer (HGT), or the movement of genes across species lines. It turns out that HGT has been widespread and important. For instance, we now know that roughly eight percent of the human genome arrived not through traditional inheritance from directly ancestral forms, but sideways by viral infection—a type of HGT.
In The Tangled Tree David Quammen, “one of that rare breed of science journalists who blends exploration with a talent for synthesis and storytelling” (Nature), chronicles these discoveries through the lives of the researchers who made them—such as Carl Woese, the most important little-known biologist of the twentieth century; Lynn Margulis, the notorious maverick whose wild ideas about “mosaic” creatures proved to be true; and Tsutomu Wantanabe, who discovered that the scourge of antibiotic-resistant bacteria is a direct result of horizontal gene transfer, bringing the deep study of genome histories to bear on a global crisis in public health.
“Quammen is no ordinary writer. He is simply astonishing, one of that rare class of writer gifted with verve, ingenuity, humor, guts, and great heart” (Elle). Now, in The Tangled Tree, he explains how molecular studies of evolution have brought startling recognitions about the tangled tree of life—including where we humans fit upon it. Thanks to new technologies such as CRISPR, we now have the ability to alter even our genetic composition—through sideways insertions, as nature has long been doing. The Tangled Tree is a brilliant guide to our transformed understanding of evolution, of life’s history, and of our own human nature.
About the Author:
David Quammen’s fifteen books include The Tangled Tree, The Song of the Dodo, The Reluctant Mr. Darwin, and Spillover, a finalist for the National Book Critics Circle award. He has written for Harper’s, The Atlantic, Rolling Stone, The New York Times Book Review, Outside, and Powder, among other magazines, and is a contributing writer for National Geographic. He wrote the entire text of the May 2016 issue of National Geographic on the Greater Yellowstone ecosystem—the first time in the history of the magazine that an issue was single-authored. Quammen shares a home in Bozeman, Montana, with his wife, Betsy Gaines Quammen, an environmental historian, along with two Russian wolfhounds and a cross-eyed cat. Visit him at DavidQuammen.com.
