One of the reasons why monkeys are unable to speak appears to be the fact that these animals lack the necessary vocal equipment. This includes special features that humans have, including the lips, tongue and larynx. Although different types of monkeys, such as chimpanzees and baboons are able to make a variety of sounds (yawning, smacking their lips, yelling, etc.) they do not seem to be able to recreate the complex sounds that are found in human speech.
