Not all canonical AAs originated and evolved at the same time. AAs with complex chemical structures, such as larger ones or those with ring-containing chains like tryptophan and other aromatic AAs, are postulated to have evolved later. On the other hand, bioinformatics analysis suggests that aromatic AAs promote ordered structure formation and folding in proteins, while aromatic AAs are present in limited proportions in IDPs. IDPs and LC domains instead contain a large fraction of charged AAs and internal repulsion from AA residues of like charges contained within the same chain makes them disordered. Therefore, the late evolution of aromatic AAs on early Earth that established an ordered structural configuration in proteins indicates that IDPs might have originated first, before folded proteins.