In his 1859 book “On the Origin of Species,” Charles Darwin envisioned evolution like a branching tree. The “great Tree of Life,” he said, “fills with its dead and broken branches the crust of the earth, and covers the surface with its ever branching and beautiful ramifications.”
Ever since, biologists have sought to draw the tree of life. The invention of DNA sequencing revolutionized that project, because scientists could find the relationship among species encoded in their genes.
In the 1970s, Carl Woese of the University of Illinois and his colleagues published the first “universal tree of life” based on this approach. They presented the tree as three great trunks.
…Eukaryotes (which includes animals), Bacteria, and Archaea (microbes). Scientists updated the tree of life in April 2016, expanding the bacteria branch with recently discovered data, thanks to “the increasing ease of DNA sequencing in the 2000s.”
More about life: Evidence of evolution that you can find on your body, Are We Really 99% Chimp? and Who was the first human?