Book Review from The Boston Globe, August 2, 2018
In 1837, Charles Darwin made a sketch: a single line at the bottom, then a branch, and another, and branches on those branches. He used that diagram to help crystallize his ideas about how species emerged and diverged from preceding forms.
That image, the tree of life, proved such a powerful metaphor, that in the 20th century it morphed from being a map of evolution into an origin story.