Modern cats diverged from their sabre-toothed ancestors early in evolutionary history to follow a separate trajectory of development, British researchers say. A study of skull shapes by researchers at the University of Bristol also showed the separation between modern domestic cats and big cats, such as lions and tigers, is likewise deeply rooted. Scientists in Bristol\'s School of Earth Sciences studied the skull shape of extinct sabre-toothed cats, modern (conical-toothed) cats and prehistoric \"basal\" cats (ancestors of modern cats). They found an early and conspicuous divergence between the modern conical-toothed cats and sabre-toothed cats, with all sabre-toothed cats being more closely related to each other than they were to modern conical-toothed cats. There followed a separation between modern small-medium cats such as the domestic cat and close relatives the cheetah, puma, ocelot, serval and lynx -- all of the genus Felinae -- and modern big cats of the genus Pantherinea such as the lion, tiger, leopard and jaguar, they said. That also happened early in their evolutionary history, researchers said. \"Our study is the first to determine the interrelationships between modern conical-toothed cats, sabre-toothed cats, and some basal cats,\" researcher Manabu Sakamoto said, noting \"our results show that differences in cat skull shape have deeply rooted evolutionary histories, first between the sabre-toothed and conical-toothed cats, and then between small-medium and large cats.\"