Before the end of the last Ice Age, fierce saber-toothed cats roamed every continent except Australia and Antarctica.
Although most people probably picture saber-toothed cats with long fangs, not all had such big teeth. One ancient cat in particular, called Homotherium latidens, had shorter canines, leading scientists to nickname it the "scimitar-toothed cat," after the short sword with a curved blade.
A recent study published in the journal Current Biology mapped the entire genome of this cat for the first time.
Based on the extinct predator's genes, the researchers determined that Homotherium was a highly skilled pack hunter, which literally chased its prey to death across large distances.
"They had genetic adaptations for strong bones and cardiovascular and respiratory systems, meaning they were well suited for endurance running," Michael Westbury, a co-author of the study and evolutionary genomicist at the University of Copehagen, said in a press release.
The cats "likely had very good daytime vision and displayed complex social behaviors," Westbury added.
These cats could pursue their prey until it was exhausted
Westbury's team pulled the ancient cat's DNA from a thigh bone they found in permafrost (perpetually frozen ground) outside Dawson City in the Canadian Yukon.
The researchers determined the fossil to be at least 47,500 years old.
An analysis of the creature's genome showed that Homotherium had at least 31 genes that coded for adaptations to help it hunt successfully during the day. Specifically, its genes suggest that Homotherium had excellent daytime vision, strong bones, and a powerful heart and lungs.
Such adaptations "may have enabled sustained running necessary for hunting in more open habitats and the pursuit of prey until their point of exhaustion," the study authors wrote.
What's more, Westbury and his colleagues found that these cats had "well-developed social behavior" and likely lived and hunted in packs similar to the way modern lions do.
These ancient cats we more abundant than scientists thought
The DNA analysis also revealed that Homotherium was more abundant than its limited fossil record suggests.
Based on the scimitar-toothed cat's DNA, Westbury's team found that the mother and father of the Homotherium that this thigh bone belonged to were genetically quite diverse from one another — more different, they concluded, than any two parents of modern cats like tigers.
To have that range of genetic diversity, the study authors wrote, there must have been a large population of Homotherium latidens roaming the world.
"Genetic diversity correlates to how many of a given species that exists," Westbury said, adding, "our best guess is that there were a lot of these big cats around."
Saber-toothed cats — including Homotherium — and modern cats share a common ancestor. But about 22.5 million years ago, the ancient cats genetically split from all other living cats to become their own group of species, according to the study authors.
The scimitar-toothed cats then diverged from their longer-toothed brethren, called smilodons, about 18 million years ago, according to a 2017 study.
The cats went extinct alongside other giant creatures at the end of the last Ice Age
Previous fossil evidence has revealed that scimitar-toothed cats had longer forelimbs than hind limbs and boasted svelt bodies built for running after prey. They chased mammoths, giant ground sloths, and other large animals during the Pleistocene era, which started roughly 2.5 million years ago and lasted until the end of the last Ice Age, about 11,700 years ago.
"This was an extremely successful family of cats. They were present on five continents and roamed the Earth for millions of years before going extinct," Ross Barnett, another co-author of the study, said in a press release.
But even these hunters couldn't overcome the environmental changes brought on by a warming world, especially when paired with increased competition with humans for limited prey.
The 2017 discovery of a 28,000-year-old Homotherium jaw bone in the UK's North Sea led researchers to conclude that these saber-toothed cats went extinct at the end of the Pleistocene, part of a planet-wide extinction that hit all the world's megafauna, including cave bears and ancient horses.
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