Right. It's not 'either - or' but all of 'em.
When one finds a deer skeleton stripped bare with the bones crunched up, scattered and bare one knows it was probably everything from bears, large cats and/or coyotes down to beetles, flies and maggots and then on down to the bugs in their gut.
"Ashes to ashes, dust to dust" is optimistic. For most creatures they are gone before they can turn to either ashes or dust.
Arf