THE TREE OF LIFE

Climbing the tree of a “dazzlingly diverse” life.

Telford, an evolutionary biologist at University College London, tells the story of the search for life’s ancestors in this fast-paced and highly entertaining examination of life forms, from LUCA—the Last Universal Common Ancestor—to Homo sapiens. The concept of the tree of life, perhaps first conceived by Aristotle, is a visual representation of relatedness, explaining how all living species, “from oak trees to orcas,” are connected. Telford works at solving what he calls “science’s greatest puzzle,” how the products of the process of evolution came to be. The tree of life is “a portal that can transport us back in time to meet our ancestors,” he writes, and his book has the feel of an amusement park ride through time as he leaps from one epoch to another, from LUCA’s beginnings 4 billion years ago to the appearance of Homo erectus 1.5 million years ago, with dozens of stops in between. Life is a “collective noun encompassing every single living thing, every species alive today and every species that has ever existed.” Telford explains the very complicated science of the ancestor search in simple terms. The 9 million species alive today are a tiny fraction of the billions of species that have ever existed on Earth. Most fossils have no remaining DNA, which is a soft tissue that degrades rapidly, at least in geological time. The oldest intact DNA found to date is 2 million years old, so using DNA to build the tree of life is useful for “only the last 0.3% of the history of the animal kingdom and just the final 0.05% of the total history of life.” That’s still a lot of life to categorize, and Telford and a worldwide community of scientists are looking for connections among species and fossil DNA to put the branches and twigs in their proper place on the tree.

From the first simple cell to today’s variety of life forms, this is the story of us—fascinating, captivating, and complex.