Speech ended not only the evolution of man, by making it no longer necessary for survival, but also the evolution of animals.
Today the so-called animal kingdom is an animal colony and we own it. It exists only at our sufferance. If we were foolish enough and could get the cooperation of people all over the earth, in six months we could exterminate every animal that sticks up more than a half inch above the ground. Already all cattle, chickens, and sheep in the world and the vast majority of pigs, horses, and turkeys—we hold the whole huge gaggle of them captive, all of them… to do with as we wish. (pp 262-263, large print edition)
Yet no one has any idea how language started.
See also: Linguist Noel Rude on Wolfe’s Kingdom of Speech
Can we talk? Language as the business end of consciousness