Chapter 3 - Building the Tree of Life: A Biodiversity Moonshot

Abstract

Why did it take over 150 years from the time of Darwin who referred to The Great Tree of Life in the mid-1800s to build the first tree of all life in 2015? With more than 2 million species already described, and many more millions undiscovered or extinct, the size of the tree is immense. As a result, the task of assembling a comprehensive tree for all life was long considered not just daunting but impossible. Put simply, building huge family trees of relationships (phylogenetic trees) is very hard, rivaling the most difficult problems in physics and astronomy. In fact, building large trees of relationships for just a few hundred species was once deemed impossible because of the mathematical challenges. For example, the number of ways that just 20 species can be connected into trees of relationships is approaching Avogadro’s number, that is a mole of trees (6.02 × 1023). For 200 species the number of possible ways for these can be assembled into a tree of relationships is greater than the estimated number of atoms in the universe. Thus, building the first tree of all named Life (all 2.3 million species) was a true “grand challenge” or a “moonshot” for all of biology. Accomplishing that moonshot required the perfect storm of algorithm development, computer power, DNA sequencing improvements, as well as international collaboration and teamwork. That perfect storm was only possible and realized in the past 10 years. Furthermore, building the first Tree of Life provides an enormously important tool for human well-being with numerous downstream applications.