Arguably the most unique ability of humans is the ability to communicate highly complex concepts, for which we need language. But language can mean many things, from sign language to writing, although the most efficient form of language we have is speech – a skill unique today to living modern humans. The apes have a remarkable capacity for language and communication: Kanzi the bonobo (fig. 1) has a working knowledge of perhaps thousands of words and Koko the gorilla understands and uses American Sign Language. But they are unable to speak. Why is this? What are differences between human and ape anatomy that allow us to produce these sounds, and what selection pressures may have driven the evolution of our highly specialised anatomy?