Well, there's a part of Hindu mythology that tells about an Asura (demon) called Tarakasura. He basically cheated Brahma to grant him two wishes.
The first wish was that the Gods would not make any being more powerful than Tarakasura.
The second wish was <drumroll>
that he could only be killed by a son of Shiva.Naturally, Tarakasura became Demon king of all three worlds, banished Gods from their world and invaded it; he had become too powerful for even gods to stop. And only Shiva's son could kill him, because apparently what Brahma promises he keeps...
Now, ain't
that interesting...
There's two (main) options if we consider this mythology more than just coincidence. The Shivans are probably analogous to "son of Shiva" as a whole, but what they are doing is a different thing. They were probably made for one task - to get rid of Tarakasura/some kind of powerful invader race out of the picture.
Option 1: They completed the task, but their masters didn't bother to get rid of the Shivans afterwards, and they evolved and revolved their own culture, reflecting their original purpose. They roam through universe, confused or non-confused, still trying to fulfill the long since fulfilled task given to them. Perhaps they are angry at Brahma for being the original reason behind all that, and thus decided "Brahma's Heart", Capella. That might just have been a coincidence, however.
Option 2: The original task is yet to be completed, so whatever it was that Shivans were made to counter still exists, and by the "run for the hills!" method used by Shivans in FS2 I'd say they are not doing too good. That would imply that there is some other species representing Tarakasura and his realm of demons, perhaps even stronger than Shivans. And perhaps they are following the Shivans...

Option 2 feels more right to me somehow, considering Volition's statements of "Shivans being just a part of a bigger problem" in universe.
Make of this what you will.

But I figure it would fit nicely into what little the

have told us about plot for FS3.
Ancients don't fit very well into role of sustainers, I think. But as I said, there are loads of mythological references in FS3, but the weird thing is that the situations might not have direct counterpart in real world mythologies. These inconsistencies might or might not be intentional, but it sure makesinterpretation hella lot more difficult...
