Yeah, I realize that this trumps everything else.You have to understand that these are people laboring under the burden of superstition and myth.
I'm just saying that there are signs of certain death that were accessible even to primitives. It doesn't take much exposure to or experience with death to know such things. I am certain that any warrior could tell you that dead people undergo certain changes, and that nobody with rigor mortis or dependent lividity ever stood up.
So sure, if you're afraid that you might be buried alive, have a bell. I was merely responding to the idea that it takes modern knowledge or technology to be sure when somebody is dead. If you're superstitious, even that is not enough. And if you're not, the advances of modernity aren't necessary. I'll bet all ancient physicians knew that if they can't hear a heartbeat, this is someone who is dead or in the throes of actively dying. No mystery.