What are molecular clocks based on?
The molecular clock is based on the mutation rate of bio molecules. This is used to deduce the time in prehistory when two or more life forms diverged.
The biomolecular data used for such calculations are usually nucleotide sequences for DNA or amino acid sequences for proteins.
The benchmarks for determining the mutation rates are often fossil or archaeological dates.
It is commonly used in molecular evolution to estimate times of speciation or radiation.