David Quammen (Spillover: Animal Infections and the Next Human Pandemic) is a popular science writer and author of 15 previous books. In The Tangled Tree, he describes recent revolutionary discoveries about the nature of life, evolution and the human race. Gene sharing, for instance, is more complex than we previously believed. The boundaries between species are blurry, to say the least. And we are probably descended from a previously unknown category of microbial life, the archaea. "It's a little like learning, with a jolt, that your great-great-great-grandfather came not from Lithuania but from Mars."
For context, Quammen begins in 1837 with Charles Darwin's familiar tree of life. He summarizes the theory of evolution, and discoveries leading up to the relatively recent field called molecular phylogenetics, "the study of evolutionary relatedness using molecules as evidence." Beginning in the late 1960s, fringe ideas from the 1920s and 1950s were taken up and developed by a creative and colorful series of theorists and researchers, including Carl Woese, Ford Dolittle and Lynn Margulis. "Such people... are of additional interest for the ways their works grew from their lives. They serve as good reminders that science itself, however precise and objective, is a human activity.... Like music, like poetry, like baseball, like grandmaster chess, it's something gloriously imperfect that people do. The smudgy fingerprints of our humanness are all over it."
Genes don't just flow from parent to child, he writes, but also "sideways across species boundaries," including species that were previously considered far removed from each other. This phenomenon is called horizontal gene transfer, and it has destroyed the old notion of distinct species neatly arranged on an evolutionary tree. Instead, it gives us a new vision of life as an interwoven thicket of heredity and relationships, with branches that converge in ways that trees limbs never do. "Horizontal gene transfer has made the history of life unimaginably more complicated than Charles Darwin could have guessed... it went beyond Darwin's thinking without negating that thinking, just as Einstein and quantum mechanics went beyond Isaac Newton's."
Quammen is an established and skillful science writer, able to convey difficult scientific ideas with the excitement of their discovery. He balances the technical details with vivid anecdotes, humor and casual charm. This is a serious and entertaining book that will fascinate anyone interested in the history and nature of life. --Sara Catterall
Shelf Talker: An acclaimed science writer tells how recent discoveries in a new field of molecular biology have overturned old ideas of evolution and human identity.