How Do We Learn To Speak

Human brains are adapted to speech.  Humans seem to have a speech "instinct."  We "automatically" absorb our language from our surrounding.

Children raised in isolation do not speak any language.

In humans, ability to speak (even speak quite well) doesn't seem to correlate very well with general intelligence.  Speech seems to be a somewhat independent element of the brain.

Williams Syndrome is an important example of this.