The physical design of the human larynx enables us to utilize a much broader range of vowels and consonants than any other mammal, facilitating sophisticated verbal communication of complex ideas.
Human speech depends not only on our special cognitive abilities but also on our possessing the appropriate organs to generate complex sound patterns. In fact, modern man’s speech-producing apparatus is quite different from the comparable systems of living nonhuman primates. Nonhuman primates have supralaryngeal vocal tracts in which the larynx exits directly into the oral cavity. In the adult human the larynx exits directly into the pharynx. This confers on man the capacity to generate a far richer phonetic repertoire than that available to a chimpanzee. Many vowels and consonants used in human language could not be reproduced by a chimp.
Michael Denton, Nature’s Destiny, pp. 239-240.
For more information about the unique properties of human beings view The Privileged Species or read Chapter 11, “Homo Sapiens: Fire Maker” in Michael Denton’s book Nature’s Destiny.