An ancient skull found in Tibet indicates that big cats originated in central Asia, and not Africa as widely thought, palaeontologists reported on Wednesday. Dated at between 4.1 and 5.95 million years old, the fossil is the oldest remains ever found of a pantherine felid, as big cats are called. It compares with the previous felid record holder -- tooth fragments found in Tanzania that are estimated to be around 3.8 million years old. "This find suggests that big cats have a deeper evolutionary origin than previously suspected," said Jack Tseng of the University of Southern California, who led the probe. Big cats, a group called Pantherinae, include tigers, lions, leopards, snow leopards and jaguars. Their evolutionary odyssey has been hotly discussed, spiced by a lack of fossil evidence to settle the debate. Tseng, accompanied by his wife and fellow palaeontologist Juan Liu, and Gary Takeuchi of the Natural History Museum of Los Angeles, made the find in 2010 in a remote border region between Tibet and Pakistan. It was found wedged in among more than 100 bones that were probably deposited by a river that exited a cliff. After three years of anatomical comparisons with other fossils, and using DNA data to build a family tree, the team is convinced the creature was a separate species. Among modern big cats, its closest relation is the snow leopard. The weight of evidence suggests that central or northern Asia was where Pantherinae originated, some 16 million years ago, according to the paper in the British journal Proceedings of the Royal Society B. They may have lived in a vast mountain refuge, formed by the uplifting Himalayas, feeding on equally remarkable species such as the Tibetan blue sheep. They then dispersed into Southeast Asia, evolving into the clouded leopard, tiger and snow leopard lineages, and later movements across continents saw them evolve into jaguars and lions. The split with Felinae -- a group that includes cougars, lynxes and domestic cats -- occurred about six million years ago. The newly-discovered felid has been called Panthera blytheae, after Blythe Haaga, "the snow leopard-loving daughter" of a couple which supports the museum in LA, the university said in a press release.