Personally, I like the Buck Godot version of humanity.
We spread across the solar system, then collapsed when a massive solar flare anomaly fried every electronic circuit in the solar system. The only group that maintained power was a benevolent research corp beneath the polar ice cap. Using that as a starting oint, humanity rebuilt and spread across the stars, eventually gene-tailoring or evolving into specialized sub-races.
They met and were inducted into the Galimaufry, the local governmental union in charge of making sure every sentient species in the area has an opportunity to communicate with its neighbors, after the human representative performed the traditional initiation rite (Singing 'I wish they all could be femthuxian girls' in front of the assembled races' diplomats. The Galimaufry doesn't take itself too seriously.)
Unfortunately, to curb humanity's propensity for meaningless wars, we were placed under the rule of Lord Thezmothet, a plant-based super-being with the most advanced technology in known space. Then the Law was created. Law robots patrol every human world, one per world, and enforce whatever the local laws are (so know what's what when traveling), though Buck lives on New Hong Kong, where there is only one law: There are no laws. It's a fun planet. The Galimaufry serves, first and foremost, as a point of exchange for cultural concepts. Some races never developed the idea of radio communication, others are incapable of seeing in less than five and a half dimensions. This gives them a venue to expand their understanding under the watchful, but mostly laissez-faire eye, of the Prime movers, the local omnipotent and omniscient space-gods.
Oddly enough, humanity's only major contribution to galactic civilization? Popsicles. Huge hit.
Ahh, Phil Foglio. Master storyteller. I wish he'd continue Buck Godot.