What kind of evidence suggests a bear killed him? Not saying it didn't happen but proof? Could he have died from a fall, a medical issue? Then animals scavenged him? Is there any evidence that he was actually killed by a bear?
I haven't seen anything that talks about what evidence they have.
But suppose you have tooth marks on the skull...
and forensic scientists can generally tell from studying an injury if it happened post-mortem (dude fell and then was eaten) or a mauling (dude was alive)
