The great Charles Darwin visualized a tree of life (pictured below) consisting of separate species springing from a distant ancestor, but what if many of these “separate species” still share significant amounts of the same genetic material? Check out, for example, this recent report by Elizabeth Pennisi titled “Shaking up the tree of life” published in the journal Science, vol. 354 (18 Nov 2016), pp. 817-821. Here is one excerpt (p. 818): “Biologists long ago accepted that microbes can swap DNA, and they are now coming to terms with rampant gene flow among more complex creatures [such as interbreeding birds and butterflies]. ‘A large percent of the genome is free to move around,’ notes Chris Jiggins, an evolutionary biologist at the University of Cambridge in the United Kingdom. This ‘really challenges our concept of what a species is.’ As a result, where biologists once envisioned a tree of life, its branches forever distinct, many now see an interconnected web.”

Darwin’s tree of life.