What Darwin Didn't Know About Evolution - National Geographic

The tree of life is an old image, going back to the Book of Revelations. But that tree drawn by Darwin was the first evolutionary tree of life. My book is about the history of that but more importantly about the way that image has been radically revised as a result of the discoveries we have made from genome sequencing in the last 40 years.

One of the most arresting statements in your book is that “we humans probably came from creatures that, as recently as 40 years ago, were unknown to exist.” Introduce us to archaea.

The archaea are a third domain of life that was unknown to exist before 1977. It was a group of organisms thought to have been bacteria. Through a microscope, they looked like bacteria, little bugs with no complex anatomy. But with genome sequencing they were revealed to be not only not bacteria, but more different from bacteria than they are from us in terms of their genomes.

Your book is as much about scientists as it is about science, and casting a huge shadow over the story is the biologist Carl Woese, whom you call “a brilliant crank.” Explain why he is so important to this story.

He was a microbiologist at the University of Illinois, in Urbana, in the middle of the American prairie, working away during the late 1960s and early 1970s. He was deeply interested in the early history of life on Earth, going way back to the beginning of cellular and pre-cellular life close to 4 billion years ago. He thought, “How in the world can I learn about that?”

He decided the way to do it would be to go inside living cells, find a single molecule common to all forms of life, pull that molecule out, sequence its genomic letters, and then collect paragraphs of those letters for one organism and another and compare them to see who was related to whom, how distantly, how closely, and the way life had diverged over billions of years. He then made the discovery that some of these creatures that looked like bacteria, were, in fact, not bacteria at all but the archaea, this third kingdom of life. That discovery got him on the front page of the New York Times on November 3, 1977.