How Did the Researchers Estimate That the Original FOXP2 Mutation

How did the researchers estimate that the original FOXP2 mutation happened 300,000-400,000 years ago?

A) by examining the fossil record
B) They found the mutation in Neandertal DNA.
C) They found the mutation in chimpanzee DNA.
D) They found the mutation in 300,000-year-old human remains.
E) using a molecular clock