Molecular clock
The 'molecular clock' is a technique which estimates when two taxa diverged in evolution. It is based on comparing the detailed structure of key molecules. The method may be done for species, or any higher taxon, such as phyla. Adjustments are made by using what is known of the fossil record. The molecular data used for such calculations is often nucleotide sequences in genome analysis, or amino acid sequences for proteins such as haemoglobin. It is sometimes called a 'gene clock' or 'evolutionary clock'.