By Will Dunham
June 4 (Reuters) - The cave lion was one of the biggest cats to ever live, prowling a huge swathe of territory from Western Europe across Siberia and into North America and hunting large prey - and perhaps even people - before going extinct around the end of the Ice Age.
New genome research reveals what made this big cat unique and how it differed from the modern lion, its smaller cousin, though the two species did sporadically interbreed. The cave lion, whose scientific name is Panthera
spelaea, died out roughly 14,000 years ago.
The researchers compared the genomes of 12 cave lions that lived from 17,000 to 148,000 years ago in places such as Russia, Austria and Canada's Yukon territory with the genomes of 20 modern lions. Cave lion DNA was extracted mostly from bones and teeth, but also from soft tissue in well-preserved frozen cubs from Siberia, where cold conditions helped preserve ancient genetic material. One of these, a female called Sparta, is among the best Ice Age specimens ever found.
"We show that cave lions were not simply Ice Age versions of modern lions, but instead represented a highly distinct evolutionary lineage," said evolutionary geneticist Love Dalén of the Centre for Palaeogenetics, a collaboration between Stockholm University and the Swedish Museum of Natural History, senior author of the study published in the journal Cell.
The study showed that the evolutionary lineages of the two species diverged probably around 1.7 million years ago during the Pleistocene Epoch. Each species possessed unique genetic variants that likely adapted them to their different habitats and behaviors. These genetic differences related to growth, vision, brain function and circulatory development.
The cave lion, which despite its name did not actually live in caves, was significantly larger and built more robustly than the modern lion. It dwelled in colder climes, favoring the open grasslands and tundras of northern Eurasia and northwestern North America. This vanished ecosystem, called the mammoth steppe in a nod to its most prominent inhabitant, resembled today's African savanna but with frigid temperatures.
"The cave lion was absolutely an apex predator, and as such filled an incredibly important and impactful ecological role," said evolutionary geneticist and study lead author David Stanton of Cardiff University in Wales. "They were one of the most widespread carnivores to ever live."
Among its probable prey were woolly mammoths - most likely young or elderly individuals - as well as woolly rhinoceroses, antelope, reindeer, horses and bison. Humans also dwelled in these regions in the Ice Age's later stages.
"While there is no clear evidence that cave lions preyed on humans, it seems highly likely that they occasionally did so. Cave paintings show that Ice Age people were highly familiar with these animals. They are often depicted with remarkable accuracy, and are usually shown without the large mane characteristic of modern male lions," Dalén said.
Other predators sharing the landscape included wolves, cave hyenas, brown bears, cave bears and the scimitar-toothed cat Homotherium. The powerful saber-toothed cat Smilodon was a more southern species, but may have come into contact with cave lions in the Yukon and Alaska regions during brief periods of Pleistocene climate warming.
The modern lion did not venture as far north as the cave lion's usual domain. But the study showed that the two species came into contact at particularly cold stretches of the Ice Age when growing continental ice sheets and expansion of the steppe tundra brought cave lions southward, causing their ranges to overlap.
"Climate appears to dictate the level of interbreeding that we see between these species," Stanton said.
The researchers said this interbreeding may have occurred in places like modern-day Iran. That region once was home to a sizable population of modern lions, though they are now largely restricted to Africa.
The warming at the end of the Ice Age contributed to the extinctions of many of the large Pleistocene animals, or megafauna, with human hunting presenting another destabilizing factor.
"Cave lions, like the rest of the megafauna at the end of the Pleistocene, were under a huge amount of pressure due to rapid changes in climate combined with increasing human population densities. The extinction of cave lions falls into the general pattern that we see of mass extinction of megafauna at this time, but for reasons that we don't completely understand," Stanton said.
(Reporting by Will Dunham in Washington, Editing by Rosalba O'Brien)
