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; we now know that roughly eight percent of the human genome arrived sideways by viral infection - a type of HGT.<br> <br>In <i>The Tangled Tree</i>, "the grandest tale in biology ... .David Quammen presents the science - and the scientists involved - with patience, candor, and flair" (<i>Nature</i>) . We learn about the major players, 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.<br> <br>"David Quammen proves to be an immensely well-informed guide to a complex story" (<i>The Wall Street Journal</i>) . In <i>The Tangled Tree</i>, 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, we now have the ability to alter even our genetic composition - through sideways insertions, as nature has long been doing. "<i>The Tangled Tree </i>is a source of wonder ... .Quammen has written a deep and daring intellectual adventure" (<i>The Boston Globe</i>) .
