I was thinking a bit about this just now. What if the only alien races that survive first contact are the ones that wipe out the other race before the other race can wipe them out? It makes a sort of messed-up half-sense when you think about it.
If you accept the possibility of aggressive intelligence in the galaxy--and there are many reasons for such, from simple terrified xenophobia to complex, highly calculated game theory to highly alien moral systems--the only safe response for humanity is to preemptively destroy any alien civilization we can. This is because whoever makes the first move in an all-out interstellar war will automatically win thanks to innovations like relativistic kill vehicles and berserker probes; they will arrive so quickly that the target cannot mount a defense. You cannot adopt a policy of not attacking unless attacked first, because by the time you know you have been attacked, it is too late to do anything except maybe launch a revenge strike before you go extinct. Furthermore, the benefits of a peaceful contact are tiny--what are the odds that any given civilization will be technologically close enough that we will both have something to offer each other? Every civilization will undoubtedly realize this and thus (nearly) every civilization will adopt the following 'interstellar foreign policy':
- Destroy any alien civilization that is detected.
- Launch all attacks from a sparsely populated, non-habitable system and abandon said system immediately after the attack is launched. (This is to avoid any humans being killed by a fail-deadly attack.)
- Attempt to mask all traces of human civilization to prevent a strike against humanity from taking place.
This obviously does not apply to Earth wars, where weapons do not travel at the speed of light, the aggressor is not guaranteed victory, and all parties already know about each other.
I only half believe it myself, but it seems eerily plausible. Perhaps we are only still alive because we have not yet been spotted, or because we are too primitive to waste valuable weapons on, or because the RKVs and berserkers have not yet arrived.
Hmm...this might be a good idea for a timeline: humanity taking its first steps into a harsh and dangerous galaxy filled with relativistic kill vehicles, self-replicating warprobes, and alien races that justify genocide with game theory.