From Grunting To Gabbing: Why Humans Can Talk
Most of us do it every day without even thinking about it, yet talking is a uniquely human ability. Not only do humans have evolved brains that process and produce language and syntax, but we also can make a range of sounds and tones that we use to form hundreds of thousands of words.
To make these sounds — and talk — humans use the same basic apparatus that chimps have: lungs, throat, voice box, tongue and lips. But we're the ones singing opera and talking on the phone. That is because over thousands of years, humans have evolved a longer throat and smaller mouth better suited for shaping sound.
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Sean, I think it is a safe bet that the physcial adaptations came first. As for the speech areas adapted from the visual areas of the cortex, well, that would make a lot of sense in a way, and could be true. I'm not a scientist, but I believe their are two visual processing areas of the brain -- the consciouss processing in the occipatal lobe and the unconscious processing in the medial-posterior side of the temporal lobe (I think).
But our language skills sort of reside all over, so it is hard to say for sure.