Grandmother Fish

In a previous life (of mine) my father-in-law, an evolutionary biologist, kept an oil painting of a fish on the wall of the living room. At every chance he would point out, to visitors or to anyone else if there were no visitors, that he kept a portrait of his distant ancestor hanging in a prominent location, pointing to the oil painting. It was funny even the third or fourth time. It isn't really true, of course, that this was his ancestor. It was a bass, more recently evolved to its present form than humans, I suspect. But it is true that the last common ancestor of humans and fish was a…