> I'd say it would be very difficult to put a hard threshold in the phylogenetic tree, where suddenly a whole subset of means of communication discretly vanishe

> I'd say it would be very difficult to put a hard threshold in the phylogenetic tree, where suddenly a whole subset of means of communication discretly vanishes. Unless the hard threshold was created by an external force, such as humans killing off or interbreeding with every other ape species capable of high level language.