The film isn't called 'Prometheus' for no reason.
The original Greek fable of Prometheus tells the following :
His actioned angered the Gods, who sent Pandora as punishment. We've all heard the term 'Pandora's box', but it was actually jars in the original story.
I think the story in the film is a sci-fi analogy of the original Prometheus tale, with some changes.
My theory is that the first engineer - the one we see creating life on Earth after his body dissolves and spreads his DNA - did so against the wishes of the other engineers he was with. They may have been experimenting with genetic and DNA for military or war purposes, whereas he wanted to create life and use it for good ................... who knows. But for whatever reason, his actions were a strict breach of what their rules were - just like the original greek Prometheus went against the wishes of the Gods.
In turn, once the engineers learnt that life on Earth was developing, they themselves set about to develop a weapon which would extinguish that life. This was again, typically, based in genetics and may have involved further trips to Earth - hence why Earth was the central planet in the 3D star map that David looked at. They created this black liquid/goo which, depending on what it interacts with, can mutate or even kill anything it touches. And just like the original Pandora jar in the greek story, this goo was stored in vials/jars.
But the engineers, like Pandora, realised that what they were developing was too dangerous and could be out of their control. So they tried to shut the jar but it was too late, and something was already on the loose. And that in effect is what we saw depicted in the hologram re-enactment, where the engineers are trying to escape from something.
The symbols written in the caves on Earth weren't invitations, but warnings to stay away.
Just some thoughts
