Large lions roamed North America and Europe as recently as 13,000 years ago, according to a new study published in Molecular Ecology. "These ancient lions were like a super-sized version of today's lions, up to 25 percent bigger," study co-author Ross Barnett, a researcher at the Ancient Biomolecules Centre at the University of Oxford's department of zoology, said in a statement. The extinct big, big cats turned out to be much more closely related to today's lions than jaguars or other living contemporaries in North America, according to the study.

To trace the genetic tree of these fearsome felines, researchers analyzed DNA from fossils from across the Northern Hemisphere – from Germany to Wyoming. They found that the Pleistocene-period (1.8 million - 10,000 years ago) lions living in Europe and Alaska were closer cousins than those living farther south in North America. The Oxford research team explains this by pointing to the Bearing land bridge, which connected Siberia and Alaska during the last ice age, allowing the cats to travel to North America from Eurasia. Ice sheets later cut off a path southward from Canada's Yukon, isolating the population to the south and eventually rendering it genetically distinct.

But after tens of thousands of years of hunting prey on the tundra, the lions, along with the mammoth and other massive mammals, died out about 13,000 years ago. "We still don't know what caused this mass extinction," study co-author Nobby Yamaguchi, a researcher at Oxford's Wildlife Research Conservation Unit, said in a statement, "although it is likely that early humans were involved one way or another."

Images of extinct lion skull from California (top), extinct lion skull from Alaska (middle) and modern lion skull from Africa (bottom); courtesy of Nobby Yamaguchi/University of Oxford