Humans are very smart and have developed the brain so they are able to speak. There is also a bone in the back of the skull called the hyoid bone which also enables us to speak. Species without this bone cannot talk. We also learned that early humans needed some form of communication for hunting and passing information, so humans developed speech. In September our Omni teacher met with a scientis named Jeffery Laitman who explained this theory.
Chimpanzees still live in the same environment as they did thousands of years ago.
Man, on the other hand, moved from his birthplace in Africa across the globe. His ability to communicate developed as a survival tool, enabling him to adapt to varying climates and conditions by communicating with other homo-sapiens. The speech developed as groups evolved and moved throughout the world. We think that chimpanzees didn't evolve to have ability to speak because they might have became mute back in the early days. Or maybe that their tongues are different shaped than humans.