Why does all life use the same 20 amino acids?

The formation of proteins on prebiotic Earth has shed light on why all living organisms use the same set of 20 amino acids to synthesise proteins. Researchers in the US found that proteinogenic amino acids or those used to make natural proteins more readily link into small peptide chains known as oligomers than those that are similar in structure than those life doesn’t use to make proteins. These chemical properties may have made them more likely to be incorporated into proteins during the evolution of the earliest life forms.