THE TANGLED TREE

A masterful history of a new field of molecular biology that has wide-ranging implications regarding “human identity, human individuality, [and] human health.”

In their evolution from a common ancestor, multiplying species branch and branch again, forming a “tree of life”: a mainstay of biology teaching for two centuries that turns out to be wrong, writes bestselling National Geographic contributing writer Quammen (Yellowstone: A Journey Through America's Wild Heart, 2016, etc.) in this impressive account of perhaps the most unheralded scientific revolution of the 20th century. It’s the result of a new area of study called molecular phylogenetics, which involves “reading the deep history of life and the patterns of relatedness from the sequence of constituent units in certain long molecules, as those molecules exist today within living creatures. The molecules mainly in question are DNA, RNA, and a few select proteins.” After admitting that this is a mouthful, the author describes three surprising discoveries that paved the way. The first revealed that genes don’t always move from parent to offspring. Sometimes organisms pass them back and forth, which is called horizontal gene transfer. Then researchers, led by the book’s central figure, biophysicist Carl Woese (1928-2012), while comparing bacterial RNA, identified a group so different that they weren’t bacteria at all but an entirely new kingdom: the Archaea. Finally, studies kept showing that bits of hereditary material simply float independently inside cells and regularly move to neighbors, other species, or even other kingdoms. No exception, the human genome is speckled with bacterial and viral DNA. The tree of life looks more like a web. An indefatigable journalist covering a revolution whose participants are mostly alive is an irresistible combination, and Quammen seems to have interviewed them all.

A consistently engaging collection of vivid portraits of brilliant, driven, quarrelsome scientists in the process of dramatically altering the fundamentals of evolution, illuminated by the author’s insightful commentary.