Only in humans is the vocal tract optimal

The abstraction of gestural communication would have removed the need for visuals,setting the stage for a transition to spoken language.That transition would have
likely come later, though.Articulate speech depends on a vocal tract of a particular shape.Even our closest ancestors, the Neanderthals and Denisovans,had vocal tracts that were not optimal,though they likely had some vocal capacity,and possibly even language.Only in humans is the vocal tract optimal.Spoken words free the hands for activities such as tool use and transport.