A composite image of the skulls of Pachycrocuta and H. erectus, left,shows how the giant hyena may have attacked the face. Beneath is a disgorged piece of an H. erectus thighbone.
The pattern of damage on some of the skulls sheds light on how hyenas may have handled them. Bite marks on the brow ridge above the eyes indicate that this protrusion had been grasped and bitten by an animal in the course of chewing off the face. Most animals' facial bones are quite thin, and modern hyenas frequently attack or bite the face first; similarly, their ancient predecessors would likely have discovered this vulnerable region in H. erectus. Practically no such facial bones, whose structure is known to us from discoveries at other sites, have been found in the Longgushan cave.
The rest of the skull is a pretty tough nut to crack, however, even for Pachycrocuta, since it consists of bones half again as thick as those of a modern human, with massive mounds called tori above the eyes and ears and around the back of the skull. Puncture marks and elongated bite marks around the skulls reveal that the hyenas gnawed at and grappled with them, probably in an effort to crack open the cranium and consume the tasty, lipid-rich brain. We concluded that the hyenas probably succeeded best by chewing through the face, gaining a purchase on the bone surrounding the foramen magnum (the opening in the cranium where the spinal cord enters), and then gnawing away until the skull vault cracked apart or the opening was large enough to expose the brain. This is how we believe the skull bases were destroyed - not by the actions of cannibalistic H. erectus.
'Course, what was probably really happening was something out of John Carpenter's The Thing, so maybe I don't wanna go.....