Spoken language is what makes us so very different from animals and birds because by the mere utterance of certain sounds, human are able to communicate and share ideas among themselves that no other living being is entire capable of doing as successfully.
Homo Sapiens first used spoken languages between 30,000 and 100,00 years ago while the first written language was found in China engraved on pottery from almost 4500 BC.
there has been various experiments that have been made in the field of language but most famous of all of them is the Forbidden Experiment that deals with studying a child that has been isolated from the outside world of normal spoken or even sign language.