The Mouse Who Spoke In A Deep Voice
FOXP2 is known as “the language gene.” When it goes wrong, as it famously did for a family in England, it can cause severe deficits in language ability. In the “KE family" in England, for instance, several family members carry a defective mutation of the gene and have trouble with grammar and writing, and with making the right face and mouth movements for normal speech. There’s a nice write-up on the gene at “Not Exactly Rocket Science”
