With class inheritance their are obviously ancestors and descendants (whatever the specific language calls them). That's the chain of class inheritance. There are no such relationships with traits; any object can be given any set of traits that are meaningful to it. If you've never read the Second Rust koan, it's worth some contemplation.
Incidentally, I was part of the original Honeywell Green team whose language design for the US DoD is now known as Ada, so I'm quite familar with the Strawman Ironman Steelman progression.