/sci/ - Science & Math

>>11388817

Question for evolutionary biologists

When we look at the phylogenetic tree of any species, we always see the name of a species at the end of one of the branches and go "oh yes, this one had a common ancestor with this other one here" and then point to where the branch veered off implying speciation.

The thing is, do we ever know what this common ancestor was? We always say, "this and this diverged from a common ancestor 5 million years ago" but do we ever know what that common ancestor was?

Is it not valid to say that that new species, through evolutionary time, became this new current species? Or do we always just say it was some different "common ancestor" that led to the more derived species?

Take, for example, whale evolution. Should I infer that basilosaurus and modern whales share a common ancestor that is unknown? Or would I be correct in saying that Basilosaurus is a more ancestral species of modern whales and eventually, through evolutionary time, became modern whales?

Like is basilosaurus a "transition" or the "common ancestor"? Know what I mean?