The burnt bodies

So, when looking closely at the burnt bodies on the trailer, they look fresh. Bodies that are burnt still decompose, and none of the bodies I saw in the trailer look decomposed in any way, only blackened.  A few look "stretched" or mutated in other ways.  Some look like they are in the process of mutating or changing into something, possibly due to exposure to the black goo.  But the feet, hands, and flesh all look like they died yesterday.  So possibly all the bodies we see in the trailer died fairly recently? 

They might simply be mummified, or some other process, but either way, it looks amazing.

Any thoughts on what they were, when they lived, and how they died?