What if in say, 15,000 B.C. vocal chords or anything like them ceased to form in humans, would our intellegence have seriously degenerated by now?
I have heard of many people born deaf with the ability to speak, I never have heard of anyone who was born with normal hearing but unable to speak. Does that happen? It takes more than just intellegence to speak I think. "Rise of the Planet of the Apes" to the contrary chimps would need more than superhuman intellegence that they don't have IOTL would they not to speak?