how did our language derive from nothing?

I'm just having a hard time grasping the idea that our complex written language of today derived from grunts or no sounds at all. I know that our brain is 2 times bigger than an apes brain for example, and 3 times bigger than a chimps but how did our language come from nothing if it wasnt given to us by a higher power? Is it all because our brain capacity is bigger, or because we have complex sweat glands so we dont have to pant like a majority of mammal species, i just cant seem to grasp that our language came from nothing in the 3.5 million years we have been said to be around, while other species which have been around way longer havent sprouted anything more than the bees dancing "language," so i just need some help or facts elaborating on how our complex communication sprouted. thank you

so these children with deaf parents didnt have any sign of language? i find that hard to believe, none of there neighbors or relatives or anything spoke around them? where did you get this information

how do you know that the large portion of the brain devoted to social interactments didnt develope in later years?