Final answer:
Molecular clocks use DNA sequences to estimate the time when species diverged from a common ancestor. Similar DNA sequences indicate a more recent divergence, while greater differences suggest a more distant past. Therefore, closeness in sequence does show how recently species diverged from each other.
Step-by-step explanation:
Molecular clocks use DNA sequences or the proteins they encode to estimate the relatedness among species and the time when they diverged from a common ancestor. The concept is based on the assumption that mutations occur at a steady average rate over time. Species with more similar DNA sequences are assumed to have diverged more recently, while those with greater differences are assumed to have diverged in the more distant past.
For example, let's say we have two species of birds. By comparing their DNA sequences, we find that they have a 98% similarity. This suggests that they diverged more recently from a common ancestor. On the other hand, if we compare the DNA sequences of two different species of mammals and find that they have only a 70% similarity, we can infer that they diverged in the more distant past.
Therefore, the closeness in sequence does provide information about how recently species diverged from each other.