I say language was an "accident" because that is what it probably was. The reason our closest relatives, the great apes, do not speak is not because they lack anything in their brains; they lack a voice. They don't have a larynx, and their tongues cannot move as freely as ours.
Taught sign languages and given other technologies with which to communicate to humans, they learn language nearly as rapidly as a child. Coco, a gorilla in California, now has a vocabulary of more than a thousand words, is learning two new words a day, and composes sentences on her keyboard.
When, for some reason or other, it could have been just a random mutation, the voice-box and flexible tongue appeared, everything changed. If there is one single charachteristic that most distinguishes human beings from other creatures, it is our capacity to speak.