TFA refers to 'non-trivial compositionality' as what's novel about how humans communicate (and how it's perhaps not as novel as we thought):

> However, the team also found examples of non-trivial compositionality, the first such discovery outside of humans.

> The first non-trivial combination was high hoot-low hoot that was translated as a distress call. But it was also used to stop other individuals’ display behaviors—dramatic, exaggerated actions or gestures bonobos perform to assert dominance or attract attention. The second was either peep or yelp in the “join” meaning paired with high hoot to form a structure used for coordinating with others before traveling. Finally, the “I would like to” peep followed by “let’s stay together” whistle was used for initiating more romantically inclined interactions bonobos are famous for indulging in.