How related genetically are all of the dolphin species swimming in the oceans? I've read that (In captivity at least) there have been born several hybrids of dolphins species (Usually a bottlenosed dolphin crossed with something else like a rough toothed dolphin or a false killer whale...I read about the "wolphin" born in Hawaii) Do the resulting hybrids mean that there had been a recent decent from a common ancestor for most of the dolphin-like animals (including blackfish, "lags" and "cephs" ) living in todays oceans? I've learned that there have been dolphin-like animals swimming around for 15 million years at least. But I find it interesting that these hybrids happen and that the hybrids themselves aren't sterile (like mules) but, like the "wolphin" mentioned above, have babies of their own. Has there been any kind of genetic comparison of the different dolphin species?
This is a complex issue so - sorry - I'm only going to provide a brief (and probably unsatisfactory) answer. The old idea that different species can't interbreed is patently untrue - in fact hybridisation is rampant and not uncommon among animals. Certain groups of animals (in mammals two particularly good examples are cats and dolphins) are particularly flexible in terms of which species can interbreed, and it essentially seems that anything goes (in fact those last two words were the title of a paper on the subject). And species don't have to be close kin to successfully interbreed, they might be in separate genera (like bottlenose dolphins and false killer whales, or harbour porpoises and Dall's porpoises) or even in distinct 'subfamilies' (like bottlenose dolphins and roughtooth dolphins, or bottlenose dolphins and false killer whales). As you note, hybridisation in dolphins has occurred between species that are morphologically distinct, and have probably been separate for 10 million years or more.
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