Spoiler: Did one half of Jones' face disintegrate because he was cut in half in a previous season (and a different timeline)?

I'd like to know why the Observers felt the need to control the past. I guess the fascinating guest star is going to explain it to us soon, but someone must be trying to change the timeline and that's what the Observers want to prevent. I guess it's the guest star.

I like how the different threads of the show are coming together now. The writing of the show is miraculous in my opinion. I don't think that it all makes sense but the show is constantly trying to stetch the limits of narratives that can be shown on television.