MOLECULAR BIOLOGY
The study of molecular biology has opened new doors to understanding relationships among different species. After discovering a universal genetic code characteristic of all living things, scientists came to understand that the sequence of DNA on the chromosomes of organisms could serve as a measure of the relatedness of species. The more sequences shared, the closer the relationship between two species and the more recently the species has diverged from a common ancestor. The fewer sequences shared, the more distant the relationship between two species, and the further in the past the species had diverged from a common ancestor. As such, accumulated changes in the DNA of organisms serves as a sort of molecular clock.