In the Study of the Evolution of FOXP2,evidence Supporting the Evolution

In the study of the evolution of FOXP2,evidence supporting the evolution of a family language disorder comes from what important link?

A) the identification of the same mutation in all patients with speech disorders
B) the family members were all lacking vocal chords
C) the disorder is common in the family
D) the identification of a single mutation in a single gene responsible for the disorder
E) the identification of multiple mutations in multiple genes responsible for the disorder