I think this is what it is all about. An ultimate twist, a cruel fate.
The Forerunners created the Flood and used it against the Precursors, wiping them out.
The Flood then evolved and turned on them.
Short, sweet, and to the point.
This is the act of barbarity described in Silentium.
Discuss.
[Edited on 08.29.2012 11:34 PM PDT]
-
Though I admit I haven't read the newest book from what I understand the flood was discovered by humans by accident. It's possible that the precursors created it or perhaps discovered it but the forerunners I believe merely examined it to understand it more, mainly to find a way to combat it more effectively. The ships that the flood spores where found on where of unknown origin which could mean precursor or possibly something else.