Meet Sparta: The 32,000-year-old frozen cave lion cub whose DNA tells the story between them and modern lions

Pulling out a frozen organism from the ice after tens of thousands of years is no less than a scientific treasure that gives a peek into what life was like back then.Extinction is often thought of as a full stop, like when a creature vanishes, and that is it. But there have been times when the frozen ground of the far north gives scientists an opportunity to study the animals we only knew from scattered bones and faded cave paintings.The cave lion is one of those animals. For a long time, they have been imagined as a bigger, shaggier, fiercer version of the lions we know today, prowling in icy lands.But a new study has a different perspective. The research, recently published in the journal Cell, carried out at the Centre for Palaeogenetics through a joint initiative of Stockholm University and the Swedish Museum of Natural History. They pieced together the cave lion's past by analysing 12 cave lion genomes gathered from across Eurasia and the northernmost reaches of North America, spanning more than 1,00,000 years, and compared them with 20 genomes from modern lions in Africa and southern Asia.Some of that ancient DNA came from old bones and teeth. But some came from surprisingly well-preserved soft tissue. The most complete specimen is a female cub known as "Sparta," which radiocarbon dating puts at around 32,000 years old. She was found in 2018 at Belaya Gora, near the Indigirka River in northeastern Siberia.According to lead author David Stanton, a lecturer at Cardiff University, "Cave lions have often been portrayed as just a larger, more rugged version of modern lions." But, he explained, "what we see in their genomes is something much more remarkable, a lineage that has been evolving independently for over a million years, accumulating its own unique biological features." The split, the team estimates, stretches back more than 1.5 million years, which is far deeper than earlier work had suggested.The researchers identified mutations found only in cave lions, along with an unusual cluster of changes in genes that belonged to brain function, vision, growth, and the circulatory system. So, these cats may have differed from modern lions not just in size but in behaviour and biology too, which matches what fossils and ancient cave art had hinted at.Yet the two lineages did not stay entirely apart. The genomes showed that the two kinds of lions bred with each other many times over tens of thousands of years.The amount of modern-lion DNA that ended up in cave lions was small, less than 5%, but it clearly happened more than once.Most interestingly, the timing matched up with the climate. Cave lions carried more modern-lion ancestry during the coldest periods, when ice sheets were at their greatest extent, and the animals likely moved south into Central and Southwest Asia, meeting modern lions there.