A four-million-year-old skull uncovered in Tibet fleshes out the fossil record of big cats and challenges theories about how and where they evolved.
The skull from the new species Panthera blytheae, a relative of the snow leopard, was excavated and described by a team led by Jack Tseng, a PhD student at the University of Southern California at the time of the discovery and now a postdoctoral fellow at the American Museum of Natural History in New York.
“This find suggests that big cats have a deeper evolutionary origin than previously suspected,” Tseng says. The announcement was made in a paper published in the Proceedings of the Royal Society B: Biological Sciences.
DNA evidence suggests that the so-called “big cats”—the Pantherinae subfamily, including lions, jaguars, tigers, leopards, snow leopards, and clouded leopards—diverged from their nearest evolutionary cousins, Felinae, which includes cougars, lynxes, and domestic cats, about 6.37 million years ago. However, the oldest fossils of big cats previously found are tooth fragments uncovered at Laetoli in Tanzania, the famed hominin site excavated by Mary Leakey in the 1970s, dating to just 3.6 million years ago.
Using magnetostratigraphy—dating fossils based on the distinctive patterns of reversals in the Earth’s magnetic field, which are recorded in layers of rock—Tseng and his team were able to estimate the age of the skull at between 4.10 and 5.95 million years old.
Spread out from central Asia
The find not only challenges previous suppositions about the evolution of big cats, it also helps place that evolution in a geographical context. The find occured in a region that overlaps the majority of current big cat habitats, and suggests that the group evolved in central Asia and spread outward.
In addition, recent estimates suggested that the genus Panthera (lions, tigers, leopards, jaguars, and snow leopards) did not split from genus Neofelis (clouded leopards) until 3.72 million years ago—which the new find disproves.
Tseng, his wife Juan Liu, and Gary Takeuchi of the Natural History Museum of Los Angeles County and the Page Museum at the La Brea Tar Pits discovered the skull in 2010 while scouting in the remote border region between Pakistan and China—an area that takes a bumpy seven-day car ride to reach from Beijing.
Liu found over one hundred bones that were likely deposited by a river eroding out of a cliff. There, below the antelope limbs and jaws, was the crushed, but largely complete remains of the skull.
“It was just lodged in the middle of all that mess,” Tseng says.
For the past three years, Tseng and his team have used both anatomical and DNA data to determine that the skull does, in fact, represent a new species. They plan to return to the site where they found the skull in the summer to search for more specimens.
The National Basic Research Program of China, the Chinese Academy of Sciences, the National Science Foundation, the American Museum of Natural History, the Smithsonian Institution (National Museum of Natural History), and the National Geographic Society funded the research.