This question already has an answer here:
There were two books in the set. Humans are living in another galaxy within an alien culture. They discover that they were grown by this other species based on DNA code beamed from Earth ages before. A group of humans are eventually given permission to make their way back to earth. During their travels they piece together the history of humanity and what befell them.
I have searched every author I can think of but can't find them. It feels so much like a Baxter novel but I don't see anything by him.