A good way to start an argument among biologists is to ask them what seems a simple question: "What is a species?" To evolutionary theorists, a species is a fundamental unit, and transitions between ...

For more on big cats, tune in to Big Cat Week, premiering Monday, Feb. 20, at 9/8c on Nat Geo WILD and learn more about the National Geographic Big Cats Initiative, a global initiative that supports ...

There are no wild ligers. Indeed, hybrids were once thought to be rare in nature—and of little consequence in an evolutionary sense. But now we know they can play an important role in speciation—the ...