Getting Rid of Precursors
 

So having Precursors in science fiction is handy they let you introduce technology above the current level of advancement, have terraforming or uplifting done in the past, and just generally add interest to your timeline

However quite often you want them to arrive, do their stuff and then get out of the way for the younger races. The standard space operatic method is for them to turn into pure psychic energy or something similarly bafflingly unphysical. High ultratech civilizations are pretty hard to wipe out so what's a more reasonable excuse?

They could withdraw from the area but while that has the advantage of actually being possible it feels somewhat implausible for a culture that gets to precursor levels of achievement just leaving. I suppose you could have them leave for the same reason the designer wants them to: after having set up everything they could leave it alone to see what the younger races do.

War is a great way to wipe out precursors but it has difficulty not leaving you another set of precursors in the same area. A war waged solely for the purpose of exterminating the precursors would work but that has a tendency of leaving glassed instead of nice t-shirt planets. I suppose if the precursor's enemies' biochemistry is sufficiently different from the precursors then their terraformed planets might be unsuited to them and they might just be ignored. They could also be eliminated while their (semi?)automated terraforming project was in it's early stages

They could also wipe themselves out by terribly lax safety rules with strangelets or whatever but that also leaves uninhabitable planets. Also it requires them to be idiots for a while and it seems hard to eliminate more than one planet or moon or space station that way.

I suppose some kind of anti-technological movement might cause them to diminish in importance as well

EDIT: The beginings of a taxonomy of precursor killers

I Internal

A Accident

B Civil War

1 Between Precursors

2 Rebellion by oppressed non-Precursors

C Withdrawal

1 Prime directive (do not interfere with species development past a certain point)

i Lensman Gambit(Need new race to exceed their current status e.g. because have hit technological wall

ii Ethical Issues

2 Technology loss

i Anti-technological movement

ii Ultra-tech leads to loss of intelligence

a Intelligence neither needed nor encouraged

b Precursors deliberately revert to presapient form (similar to Lensman Gambit)

3 Virtual Reality

4 Area of setting does not support/is not considered suitable for precursors

i Resource depletion

a Renewable

b nonrenewable

ii Lack of high energy resources nearby

iii Signal delay

iv Breakdown of key technology (such as FTL)

5 Pocket universe/ascension/otherwise leave normal space

6 Religious mandate to leave

7 Population issues

i Failure to recover from population crash. (though the cause of the crash may be external the failure is what really removes the precursors.)

ii Low birthrates plus something happening to extremely old precursors

a Die or leave due to boredom

II External

A Hostile action

1 Gengineered disease

2 War

i Unrecoverable total war(strangelet or black hole weapons)

ii Longterm recoverable war

iii Precursors were located in space so war does not damage planet

3 Preemptive flight from enemies

B Natural

1 Some kind of nasty natural thing like a black hole or strangelet asteroid comes along and wrecks the local precursors

Re: Getting Rid of Precursors
 

I think that "being wiped out by machine intelligence/themselves/galactic cycles" is even more common, Benford's Galactic Center books, Traveller, Mass Effect, Hyperion, just off the top of my head all have this trope.

Re: Getting Rid of Precursors
 

Yeah that's pretty common as well and I don't have any statistical basis for which is more.

The question is why isn't the thing that wiped them out hanging around where the precursors used to be. (not that those examples necessarily lack a reason.)

Re: Getting Rid of Precursors
 

Gengineered diseases might work.

Re: Getting Rid of Precursors
 

Doomsday machines that only turn on when exposed to a pre-programmed threat? Your new species doesn't qualify for some reason.

Re: Getting Rid of Precursors
 

They're still out there, but they withdrawn into their virtual reality playgrounds and never leave except for reasons of PLOT. Seek them out at your peril, for they will almost certainly treat you like a colony of ants or some other pest fouling up their home.

Re: Getting Rid of Precursors
 

That works really well. It doesn't stop someone else from killing them but it does stop them from moving in and if they were doing the whole shepherd of new lifeforms thing it makes sense that they would somehow immunize the younger races.

It's hard to fit together a culture that travels immense distances and spends large amounts of resources terraforming and stuff with one that sticks around in virtual reality. I suppose a cultural change after they do all the stuff they need to could accomplish it.

Re: Getting Rid of Precursors
 

This is usually the way this trope works. Something wiped them out and it's just now that galactic civilization has re-triggered the apocalypse machines. Duh, duh, dun!
That seems to be the case with the whole Involved->Sublimed progression in the Culture books.

Re: Getting Rid of Precursors
 

I kind of find it improbable that an entire civilization would become completely
bored of reality and live in VR/ascend/sublime.

... Of course I don't need an entire civilization to do it, just the local group.

Re: Getting Rid of Precursors
 

Have you read The Stone Canal or The Cassini Division? The fast folk are pretty plausible, IMO.