Language has long been considered a uniquely human trait, with features that mark it out as distinct from the communication of all other species. However, research published in Science has uncovered the same statistical structure that is a hallmark of human language in humpback whale song.
"Whale song is not a language; it lacks semantic meaning. It may be more reminiscent of human music, which also has this statistical structure, but lacks the expressive meaning found in language."
What the author is saying here is that you can't split whale songs into pieces and say "this piece means [thing], that other piece means [another thing]". You can't do it with human music either. And yet it's an essential component of language, all languages attested out there work with those units (called morphemes).