Darwin’s seminal ideas provide a qualitative basis for understanding biological evolution.
Yet, quantitative characterization of evolution involves formidable challenges. For
example, there is a large uncertainty in the total number of species existing on Earth,
with estimates ranging from 2 to 100 million [1]. Furthermore, only a small fraction of
all of the extinct species is presently known [2]. Biological evolution remains one of the
deepest and most elusive problems in science.