The wild and woolly world of hybrids is setting evolutionary ideas back on their heels. Species simply don’t arise in the way the evolutionary tree proposes.
What do you get…when you cross a zebra with a horse? Give up? Why, a zorse, of course! How about crossing a polar bear and a grizzly? If you said “pizzly,” you’re catching on! Do you think I’m joking about these names? Guess again.
These are real examples of separate species that can breed and produce unique hybrid babies. Biologists have known about them for a long time, but until recently they thought hybrids were oddities. They usually observed these mixes in captivity, not in the wild—strange hybrids like the ones above, or wholphins (mix of a bottlenose dolphin and a false killer whale) and geeps (mix of a goat and a sheep). New, inexpensive techniques of DNA analysis have now enabled scientists to test a variety of wild creatures, and they have discovered that hybridization seems to occur all the time in the wild.
This find is “challenging evolutionary theory,” Science journal admits in “Shaking Up the Tree of Life” (November 2016). Why such dramatic language for a normally reserved journal? For one thing, hybridization turns the concept of species upside down—and the origin of species is ground zero for evolution. Second, it turns the tree of life into spaghetti.
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