Scientists have found that an Atlantic bottlenose dolphin has bred with a false killer whale to produce a hybrid referred to as a "wolphin".
Although false killer whales and Atlantic bottlenose dolphins are different species, they are classified within the same family by scientists.
Scientists identify a species in terms of whether members of the two groups can interbreed and produce fertile offspring. If they cannot, like cats and dogs which cannot interbreed, or horses and donkeys which can interbreed but whose offspring (mules) is infertile, they are said to be reproductively isolated and are therefore regarded as separate species.
If this "wolphin" is fertile, however, then either the concept of species loses a lot of its meaning or we must allow that at least some kinds of whales and some kinds of dolphins are really the same species.
A revision of the concept of species would have interesting implications for human evolution. There are numerous fossil hominids which have been placed in disparate species on the basis of morphological differences which may or may not warrant the separation. Morphology, after all, is a precarious criterion for taxonomic distinctions. All the domestic dogs around the world, from Chihuahuas to Great Danes, are members of the same species.
If the various hominids were indeed interfertile then the rationale for placing them in different species disappears. As it is, the only rationale for separating them is that paleontologists assume that they have evolved over time one from the other, and that, being separated by vast amounts of time, they must have been reproductively isolated.
If, however, it were to turn out that they were all members of the same species it would certainly make life difficult for evolutionists. They would then be confronted with a relatively abrupt speciation event in which ape-like hominoids transitioned to Homo sapiens while leaving very little evidence of intermediary forms.
The story of human evolution, like evolution in general, is far from settled.