Could sky burial be the elevating of bodies on platforms supported with posts - similar to some American Indian tribes?
I think it is ritualizing the process of vultures consuming corpses in the wild, which happens naturally.
People who inhabit inhospitable environment where trees are scarce and whose life-style is nomadic appear to adopt this ritual.
In Siberian tundra, there are people called Chukchis. When a Chukchi dies, his body is carried out to the open plain, and its trunk is cut up open, so that any scavenging animals can easily devour the body.
That was my first impression as well..
Thanks to easonc52 for the link.. (post#8)..
Well done explanation of Tibetan burial rites, and very informative..