With the help of a prehistoric cub carcass found frozen in Siberia, new research has shown that the extinct cave lion was a separate species to the modern-day lion. It also suggests that this ferocious Ice Age predator was divided into a western and eastern subspecies.

The cave lion was once found across much of northern Eurasia, Alaska, and the Yukon Territory throughout the Late Pleistocene until it fell into extinction some 14,000 years ago. Scientists have long-debated where these cave-dwelling big cats fit onto the family tree, with some suggesting they are subspecies of modern lions, others suggesting they're a separate species entirely, while some even argue they may have been more closely related to tigers. 

Reported in the journal Scientific Reports, researchers from the Centre for Palaeogenetics in Sweden recently took a deep dive into the evolutionary history of cave lions by comparing the mitochondrial genomes of 31 specimens found across their entire prehistoric range. One of these individuals was “Spartak”, a cave lion cub that remained near-perfectly preserved in the icy depths of Siberia. At the ripe old age of 28,000 years, Spartak is said to be the best-preserved Ice Age animal ever discovered.

This revealed that cave lions (Panthera spelaea) were indeed a separate species to modern-day lions (Panthera leo) found today in sub-Saharan Africa. It also showed that the cave lion diverged from a common ancestor they shared with modern lions roughly 1.85 million years ago, before subsequently splitting into two different subspecies around half a million years ago.

One of these subspecies lived in Europe while the other is known as the Beringian cave lion, which once lived in Yakutia in Northern Asia, Alaska, Yukon Territory, and the land bridge that used to cross between northern Eurasia and America. 

The cave lion is believed to have been slightly larger than today’s lions. Cave art from the time also indicates that these species might not have had a mane. It’s also apparent there were physical and behavioral differences between the two subspecies. Analysis of the specimens’ skulls and jaws has shown that the Beringian cave lions were notably smaller than the European cave lions. Building on previous work on cave lion diets, the researchers also argue that Beringia lions most likely hunted bison and horses, while the European cave lions preyed on reindeer. 

“We are now continuing with more genetic analyses, where we aim to sequence complete nuclear genomes from several specimens, in order to investigate what genes made the cave lion a cave lion,” David Stanton, lead author and a former Marie-Curie Fellow at the Centre for Palaeogenetics, said in a statement.