A Different View
by An Ordinary Man (the novel)
“Richard was hard at work an hour later when his phone rang. He had decided to revisit the definition of species. Even Darwin hadn’t been certain if species were just “well-marked variations” and the definition of the word had always appeared to Richard as more assumed than understood. Traditionally, the establishment of a new species was represented as a branching of the tree of life; a relatively clean, and essentially irreversible, event. The branches were never depicted as reconverging, much less merging with a different branch. But why not? As long as there was reproductive compatibility, it should be theoretically possible.
In his mind, a species was sort of like how rain water backed up along the curb when it ran into an obstacle; rather than a separate tributary diverging from the main stream, it might send out a new stream on a new course, or it might just widen and backup against the obstacle before eventually breaking through it and continuing on its original path. The new stream might become a new species, but it might also peter out or even rejoin the original stream further down the hill, and the widening pool would just be increased variation in what the particular animal looked like for a period of time.”
Charles Darwin included a single illustration (above) in his 1859 treatise, a rather simple diagram illustrating his principle that life diverges as it perseveres in the face of changing conditions, leading to the formation of new species over time. Darwin saw life as growing upwards and dividing like a tree while Richard saw it more as flowing downhill, like water. He wondered if the “tree of life” might not be more complicated, especially when looking at the formation of species within a genus. He was thinking in terms of this:
[N.B. the author sketched a version of this back in the early ’80s, while still a graduate student in biology in Woods Hole, MA. He had never seen anything similar to what he had in mind at the time.]