Decades ago I read a short story in an anthology where one of the first human exploration ships was out traveling to another star system when an extremely advanced alien space ship basically pulled them over to make first contact.
The aliens were extremely arrogant at first and telling the humans to stay in their own little area until eventually it came out that they were suspiciously similar genetically to humanity. And that humans had in fact evolved from the waste products one of the aliens ships had dumped on Earth way back.
The aliens then immediately ran away for unknown reasons. Humanity tried to follow them only to find that the aliens were completely avoiding them to the point of evacuating entire colonies. They eventually run into a different species that tells them that because of the aliens own laws anything derived from them is afforded specific rights. Rights that the aliens really don't want to give humans.
The humans eventually take the case to inter galactic court and basically win an extreme version of child support.
The final reveal is that the narrator of the whole story had no stake in the process because it was a robot the entire time and didn't evolve at all.
I believe it was one of those old pulp stories that Baen collected and published as anthologies. But I've read through all the ones I have access to and can't find it so that might be entirely wrong.