They do, but written records are only about five thousand years here. Ours a good deal older.

Prior to that seem to be mostly material remains, and fragmented ones, but I believe you're right that bone structure is only human. The various earths seem to be more or less human only.

[ Barring mutants, but he knows enough to not offer that. Aliens, too, which he doesn't entirely understand, but all seem fairly recent. ]