Other than survival and development, the thing that bothers me with evolution is why only one race can speak?
This is an anthropocentric prejudice more than a fact. It is a residue of the theistic bias that we are somehow separate from the animal world.
Many animals communicate and the higher in intelligence they are, the more organized those communications can be but for humans complex language is a relatively recent phenomenon and a consequence of a convergence of fortunate adaptive characteristics.
My personal argument is that we were a primate with *parroting* (oral mimicry) behaviors that gave our species an adaptive (fitness) advantage. We used it to defend against larger predators and as a lure for smaller prey. As a species we were more like modern chimps and baboons that bonobos. The fossil evidence of the human mouth and its consistent form supports this assertion but does not prove it
Anyway were began at some point systematizing our sound forms with objects as our memory developed and memetic record keeping behaviors evolved. This trend developed into complex language over a period of tens of thousands of years with the most important advances in language being in the last 10 to20 thousand.
However we have found that many species can *learn* language even if they have more trouble forming our words from mina birds to elephants. Complex human language evolved and as it evolved it gave our species more and more of an advantage to rise to the pinnacle of the food chain but it can be looked at as simply a form of evolutionary fitness.