They aren't the oldest life form in existence, nor are they the most powerful. Humans haven't mastered interstellar travel in my universe, they were just fortunate enough to live on the planet where our war ended.

[Perhaps the war was about to end anyway, and the abundance of Ore-13 on Earth sped up the dissolution of the army structures. Perhaps it was a coincidence that so many parties converged onto the same place.]

Perhaps this ship picks up life forms with with is is familiar - particularly human.