• The study of similarities and differences in the proteins and molecules that control life processes.
  • Some important molecules are highly conserved among species, so slight changes can cause death.
  • If variations occur outside of these molecules functional region they are called neutral.
  • So their accumulation is not affected by natural selection and occur at a fairly regular rat.
  • Scientists can study the DNA base sequence or order of amino acids in a protein and estimate the time at which the 2 species last shared a common ancestor.