In the Section "Investigating Life: Clues to the Origin of Language",how

In the section "Investigating Life: Clues to the Origin of Language",how did the researchers estimate that the original mutation occurred 300,000-400,000 years ago?

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