Imagine that you have the dna sequences from the intron of a gene in three species called a, b, and
c. species a and b are most closely related, while c is more distantly related. the sequences of a and b differ by 18 base pairs, a and c differ by 26 base pairs, and b and c differ by 28 base pairs. fossils show that species a and b diverged about 1.2 mya, but there is no fossil evidence as to when the most recent common ancestor of all three species lived. use the genetic data to estimate that date. what assumptions are you making to get this estimate?