Chapter 2 - History of the Modern Concept of the Tree of Life

Abstract

Everyone seems to understand the concept of one’s own family tree of relationships. Similarly, biologists talk about the relationships among species of our planet in the same basic way. The concept of trees of relationships among organisms and the idea that all species on Earth are part of a great Tree of Life dates to the time of Darwin. Darwin’s work inspired other scientists to try to draw rudimentary trees of life illustrating these connections. Although the concept of a branching Tree of Life that connects all species dates to the mid-1800s, the field or science of building trees is very recent. For well over 100 years after Darwin, researchers depicted relationships among species based on their gut feeling as to how organisms were related. These hand-drawn trees of relationship were typically based on a lifetime of study of a particular group of organisms, whether it be fungi, plants, or animals. It was not until the mid-1900s that rigorous, repeatable methods of building trees of relationships (termed “phylogenetic trees”) were introduced. In fact, it was not until the end of the 1900s that phylogenetic trees could be built routinely using characters measured from organisms, special algorithms, and computer programs. Thus, building trees or phylogenies as they are called is a very young field of scientific inquiry. Yielding powerful insights ranging from medicine to agriculture and conservation, trees of relationships are now a fundamental part of all of biology.