So, the battered head, rubble and dead SJ. Trouble on the SJ planet, yes? Disc

We can see that the huge humanoid head appears to be damaged, or at least weathered / old, and we've seen scenes which depict rubble, a (seemingly) dead SJ. And the crashing derelicts in the trailer. What does this mean? War on the SJ home world? Is the species dying out, at war with each other or have the xenomorphs infected them? Are they diseased? Has the Prometheus and it's crew caused the apparent ruin, or were the SJs in trouble before they arrived?