Suppose that two species of fish (species A and B) differ by ten substitutions in their globin genes, and that these fish diverged 5 million years ago (based on biogeographical evidence).A third species (species C) differs from species A by 40 substitutions.Assuming the molecular clock has been operating, species A and C must have split from each other _______ million years ago.
A) 5
B) 10
C) 20
D) 40
E) More information is required to answer this question.

Question

Quizplus · Accepted Answer

Assuming a constant rate of molecular evolution, if species A and B diverged by 10 substitutions in 5 million years, this is an average rate of 2 substitutions per million years. Thus, if species A and C differ by 40 substitutions, they must have diverged 20 million years ago (40 substitutions / 2 substitutions per million years).

Suppose That Two Species of Fish (Species a and B)